paige's+rock+and+mineral+page

2012 National Science Olympiad Rock and Mineral list
1. Albite [Plagioclase Group] 2.Almandine [Garnet] Almandine is one [|end-member] of a mineral [|solid solution] series, with the other end member being the garnet [|pyrope]. The almandine crystal formula is: Fe3Al2 (SiO4)3. [|Magnesium] substitutes for the [|iron] with increasingly pyrope-rich composition. Almandine, Fe2+3Al2Si3O12, is the ferrous iron end member of the class of garnet minerals representing an important group of rock-forming [|silicates], which are the main constituents of the Earth's [|crust], [|upper mantle] and [|transition zone]. Almandine crystallizes in the cubic [|space group] Ia3d, with unit-cell parameter a ≈ 11.512 Å at 100 K.[|[2]] Almandine is [|antiferromagnet] with the [|Néel temperature] of 7.5 K. It contains two equivalent magnetic sublattices [|[3]] 3. Amazonite [Microcline] 4. Apatite 5. Aragonite 6. Augite 7. Azurite ||
 * Luster is vitreous to dull if weathered.
 * Color is usually white (Albite is derived from the same root word as albino) or colorless but can be shades of blue, yellow, orange and brown.
 * **Transparency** crystals are translucent to opaque and only sometimes transparent.
 * **Crystal System** is triclinic; bar 1
 * **Crystal Habits** include blocky, tabular and platy crystals. The typical crystal has a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. A variety called Cleavelandite forms very thin platy crystals that can grow rather large (15+ cm across) but can maintain an even thickness of only a few millimeters. Twinning is almost universal in Albite. Crystals can be [|twinned] according to the Albite,Carlsbad, Manebach and Baveno laws. Albite is a common constituent of granitic and syenite rocks. Can also be massive.
 * **Cleavage** is perfect in one and good in another direction forming nearly right angled prisms.
 * **Fracture** is conchoidal.
 * **Hardness** is 6 - 6.5.
 * **Specific Gravity** is approximately 2.61 (average)
 * **Streak** is white.
 * **Associated Minerals** are **[|quartz], [|tourmaline]** and **[|muscovite]**.
 * **Other Characteristics:** index of refraction is 1.53. Lamellar twinning may cause a grooved effect on cystal surfaces that appear as striations. Some Albite may show opalescence due to twinning and is referred to as moonstone.
 * **Notable Occurrences** includeLabrador,Canada and theScandinavian Peninsula.
 * **Best Field Indicators** are occurence, crystal habit, twinning, striations, density and index of refraction.
 * Almandine** (pronounced [|/ˈælməndɪn/] ), also known incorrectly as **almandite**, is a species of mineral belonging to the [|garnet] Group. The name is a corruption of alabandicus, which is the name applied by [|Pliny the Elder] to a stone found or worked at Alabanda, a town in Caria in [|Asia Minor]. Almandine is an iron alumina garnet, of deep red color, inclining to purple. It is frequently cut with a convex face, or en [|cabochon], and is then known as [|carbuncle]. Viewed through the [|spectroscope] in a strong light, it generally shows three characteristic absorption bands.
 * Description ** Amazonite is popular in jewelry and decorative objects as well as specimens for mineral collectors. It is usually light green to blue green and is found in granite and pegmatites. It has a range of 5 to 6 on the Mohs Scale.
 * Location ** Large prismatic crystals are found in the Pike’s peak area of Colorado, the ILmen mountains of Russia, they can also be found in Madagascar, and Brazil. The specimens from Colorado are sometimes found with smoky quartz, orthoclase, and Albite. When this is the case the value of the specimens is much higher.
 * Mineral Properties ** **Chemical formula:** KAlSi3 O8, potassium aluminum silicate. **Color(s):** light green to blue green **Streak:** White**Luster:** vitreous**Transparency:** translucent to opaque**Crystal** **system:** triclinic **Crystal** **Habits:** include blocky, or tabular crystals. Crystals are close to rectangular or square cross-section; Twinning is common.**Specific Gravity:** About 2.5 depending on the specimen **Hardness (Mohs):** 6 to 6.5**Cleavage:** perfect in one and good in another direction forming nearly right angled prisms. **Fracture:** conchoidal **Uses:** Mineral Specimens, jewelry and ornamentals**Associated Minerals:** quartz, muscovite and plagioclase feldspars. **Location:** Includes Pikes Peak region of Colorado in the USA; Russia; Brazil; and Madagascar.
 * **Color** is typically green but also yellow, blue, reddish brown and purple.
 * **Luster** is vitreous to greasy and gumdrop.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System** is hexagonal; 6/m
 * **Crystal Habits** include the typical hexagonal prism with the hexagonal pyramid or a pinacoid or both as a termination. Also accicular, granular, reniform and massive. A cryptocrystalline variety is called //collophane// and can make up a rock type called phosphorite and also can replace fossil fragments.
 * **Cleavage** is indistinct in one basal direction.
 * **Fracture** is conchoidal.
 * **Hardness** is 5.
 * **Specific Gravity** is approximately 3.1 - 3.2 (average for translucent minerals)
 * **Streak** is white.
 * **Associated Minerals** are **[|hornblende], [|micas], [|nepheline]** and **[|calcite]**.
 * **Other Characteristics:** An unusual "partially dissolved" look similar to the look of previously sucked on hard candy.
 * **Notable Occurrences** includeDurango,Mexico;Bancroft,Ontario;Germany andRussia.
 * **Best Field Indicators** are crystal habit, color, hardness and look.
 * **Color** can be white or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue.
 * **Luster** is vitreous to dull.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System** is orthorhombic; 2/m 2/m 2/m
 * **Crystal Habits** include **[|twinned]** hexagonal prismatic crystals as well as a diverse assortment of thin elongated prismatic, curved bladed, steep pyramidal (spiked) and chisel shaped crystals. A branching tree, coral or worm-like delicate form is called **//"flos ferri"//.** Can also be compact, granular, radially fibrous and massive. Its massive forms can be layered, coralloid, pisolitic, oolitic, globular, stalachtitic and encrusting. Aragonite is a constituent of many species' shell structures. A layered sedimentary marble like formation is called Mexican Onyx and is used for carvings and ornamental purposes. Calcite pseudomorphs of aragonite crystals and formations are common.
 * **Cleavage** is distinct in one direction (pinacoidal).
 * **Fracture** is subconchoidal.
 * **Hardness** is 3.5-4
 * **Specific Gravity** is 2.9+ (average for non-metallic minerals)
 * **Streak** is white.
 * **Other Characteristics:** aragonite effervesces easily in cold dilute hydrochloric acid, is strongly birefringent, is **fluorescent** and its refractive index is 1.7.
 * **Associated Minerals** include **[|gypsum], [|barite], [|smithsonite], [|malachite], [|calcite], [|serpentine], [|sulfur], [|celestite], [|zeolites], [|quartz], [|clays], [|dolomite], [|limonite], [|chalcopyrite]** and **[|wulfenite]** among many others.
 * **Notable Occurrences** include Aragon, Spain (its type locality and from where it gets its name); Morocco; Bastennes, France; Girgenti, Sicily; Alston Moor and Cleator Moor, **Cumberland, England**; Baja California, Mexico (Mexican Onyx); **Tsumeb, Namibia**; Carinthia, Austria; Leadhills, Scotland; Harz Mountains, Germany and in several localities in the Southwestern United States.
 * **Best Field Indicators** are crystal habits, single plane of cleavage and reaction to acid.
 * **Color** is dark green, brown and black
 * **Luster** is vitreous to submetallic and even dull.
 * **Transparency** crystals are transparent to mostly translucent or opaque.
 * **Crystal System** is monoclinic; 2/m
 * **Crystal Habits** include short prismatic, rarely tabular crystals. The square cross section is distinctive in the prismatic crystals. Also compact, granular, columnar, lamellar and fibrous(rare).
 * **Cleavage** is perfect in two lengthwise directions at close to right angles.
 * **Fracture** is uneven.
 * **Hardness** is 5 - 6
 * **Specific Gravity** is approximately 3.2 - 3.6 (slightly above average)
 * **Streak** is greenish white.
 * **Other Characteristics:** The basal parting is prominent.
 * **Associated Minerals** are **[|olivine], [|biotite], [|nepheline], [|albite], [|apatite], [|serpentine], [|leucite]** and **[|hornblende]**.
 * **Notable Occurrences** include Grand Co, Colorado, St. Lawrence Co., New York and Tillamook, Oregon, USA; Eifel, Germany; Mt. Vesuvius, Italy; France and the Bohemian regions of Europe.
 * **Best Field Indicators** are crystal habit, associations, color, parting and cleavage.
 * **Color** is azure, deep blue or pale blue if found in small crystals or crusts.
 * **Luster** is vitreous to dull depending on habit.
 * **Transparency:** Transparent if in thin crystals, otherwise translucent to opaque.
 * **Crystal System** is monoclinic; ** 2/m .**
 * **Crystal Habits** crystals are irregular blades with wedge shaped terminations. Also, aggregate crusts and radiating, botryoidal, nodular and earthy masses.
 * **Cleavage** is good in one direction and fair in another.
 * **Fracture** is conchoidal and brittle.
 * **Hardness** is ** 3.5-4 .**
 * **Specific Gravity** is ** 3.7+ ** (heavier than average).
 * **Streak** is blue.
 * **Associated Minerals** are numerous and include **[|malachite] [|limonite], [|calcite], [|cerussite,][|quartz], [|chalcopyrite], [|native copper], [|cuprite], [|chrysocolla], [|aurichalcite], [|shattuckite], [|liroconite], [|connellite]** and other oxidized copper minerals.
 * **Notable Occurrences** include numerous localities worldwide, but special localities produce some outstanding specimens especially from Lasal, Utah; Bisbee, **[|Arizona]** and New Mexico, USA; **[|Mexico];** Tsumeb, Nambia; Shaba, Congo; Toussit, Morocco; Australia and in many locations in Europe.
 * **Best Field Indicators** are color, softness, crystal habits and associations.

What is Bauxite?

 * Bauxite is a rock composed mainly of aluminum oxide and aluminum hydroxide minerals. These might include: gibbsite, boehmite and diaspore. The rock usually includes other materials such as iron hydroxides, clay, silt and free silica. It most often occurs as a residual soil material in tropical and subtropical areas. It is the primary source of aluminum. ||
 * === Uses === || Bauxite is the most common ore of aluminum. It is also used as an abrasive, however, this use is now being replaced by synthetic materials. ||
 * === Color === || white, gray, yellow, red ||
 * === Streak === || normally white but may streak other colors if the specimen is stained ||
 * === Luster === || dull to earthy ||
 * === Diaphaneity === || translucent ||
 * === Cleavage === || because bauxite is a mixture of gibbsite, boehmite and diaspore, it has no cleavage properties of its own ||
 * === Hardness === || 1 to 3 ||
 * === Specific Gravity === || 2 - 2.5 ||
 * === Distinguishing ===

Characteristics
|| pisolitic structure, color ||
 * === Crystal System === || Bauxite is a mixture of Diaspore (orthorhomic), Gibbsite (monoclinic), and Boehmite (orthorhombic) ||
 * === Chemical Classification === || oxide / hydroxide ||
 * === Chemical Composition === || gibbsite, Al(OH)3 boehmite, AlO(OH) diaspore, AlO(OH) ||

9. Barite 10. Beryl 11. Biotite [Mica] 12. Bornite 13. Calcite 14. Celestite 15. Chalcopyrite 16. Copper 17. Corundum 18. Diamond 19. Dolomite 20. Epidote 21. Feldspar [Orthoclase Group] 22. Fluorite 23. Galena 24. Goethite/ ** Limonite ** 25. Gold 26. Graphite 27. Gypsum [Alabaster] **28**. Gypsum [Satin-Spar] 29. Gypsum [Selenite] 30. Halite 31. Hematite 32. Hornblende 33. Kaolinite 34. Lepidolite 35. Magnetite 36. Malachite 37. Muscovite [Mica] 38. Olivine 39. Opal 40. Pyrite 41. Quartz [Agate/Onyx] Onyx Agate **VARIETY OF: Crypto-crystalline [|Quartz], SiO** ** 2 ** 42. Quartz [Amethyst] 43. Quartz [Chalcedony] 44. Quartz [Citrine] 45. Quartz [Crystal] 46. Quartz [Jasper] 47. Quartz [Milky] 48. Quartz [Rose] 49. Rhodonite 50. Silver 51. Sodalite 52. Sphalerite 53. Staurolite 54. Sulfur/Sulphur 55. Talc 56. Topaz 57. Tourmaline Group The four most common and well known tourmalines are distinguished by their color and transparencies. **[|Elbaite]** is the gemstone tourmaline and comes in many varied and beautiful colors. It is transparent to translucent and is highly prized as minerals specimens and as gemstones. Elbaite is easily the most colorful of all the **[|gemstones].** The iron rich **[|schorl]** is the most abundant tourmaline and is black and opaque. It is a common accessory mineral in [|igneous] and metamorphic rocks and can form nice crystals. Although too opaque to be used as a gemstone, schorl is used as an ornamental stone when found as **[|inclusions]** in **[|quartz],** a stone is called "//tourmalinated quartz//". Usually when someone refers to tourmaline they are referring to either elbaite or schorl. The two other more common tourmalines; **[|dravite]** and **[|uvite]** are much less common than elbaite or schorl, but they are getting noticed for their beautiful specimens. Some of dravite's crystals are nicely formed, translucent brown and they can reach a rather large size. Uvite is a green translucent to opaque tourmaline that is growing in popularity and is being cut as a gemstone. 58. Tremolite 59. Ulexite ** Metamorphic Rocks ** 75. Rhyolite - Igneous Rock Type: Extrusive volcanic
 * **Color** is variable but is commonly found colorless or white, also blue, green, yellow and red shades.
 * **Luster** is vitreous.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is orthorhombic; 2/m 2/m 2/m
 * **Crystal Habits** include the bladed crystals that are dominated by two large pinacoid faces top and bottom and small prism faces forming a jutting angle on every side. There are many variations of these faces but the flattened blades and tabular crystals are the most common. If the pinacoid faces become diminished or are absent, the resulting prismatic crystal has a rhombic cross section. Also scaly, lamellar, and even fiberous.
 * **Cleavage** is perfect in one direction, less so in another direction.
 * **Fracture** is conchoidal.
 * **Hardness** is 3 - 3.5
 * **Specific Gravity** is approximately 4.5 (heavy for translucent minerals)
 * **Streak** is white.
 * **Associated Minerals** are numerous but significant associations have been with **[|chalcopyrite], [|calcite], [|aragonite], [|sulfur], [|pyrite], [|quartz], [|vanadinite], [|cerussite]** and **[|fluorite]** among many others.
 * **Other Characteristics:** green color in flame test (see above).
 * **Notable Occurrences** includeOklahoma,Connecticut andColorado,USA;England andGermany.
 * **Best Field Indicators** are crystal habit, flame test and density.
 * **Color** is varied and includes emerald green, blue to blue-green, yellow, greenish-gold, red, colorless and pink.
 * **Luster** is vitreous.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System** is hexagonal; ** 6/m 2/m 2/m **
 * **Crystal Habits** typically include the hexagonal prism with pincoid terminations. The terminations are often modified by many different pyramidal faces which can sometimes produce a rounded termination in the rough shape of a used pencil eraser.
 * **Cleavage** is imperfect in one direction (basal).
 * **Fracture** is conchoidal.
 * **Hardness** is ** 7.5 - 8 .**
 * **Specific Gravity** is approximately ** 2.6 - 2.9 ** (average)
 * **Streak** is white.
 * **Other Characteristics:** Faces on large crystals are often pitted, striated lengthwise and rough.
 * **Associated Minerals** include **[|micas], [|quartz], [|euclase], [|calcite], [|tourmalines]** and some **[|feldspars]**.
 * **Notable Occurrences** includeColombia and some African localities for emerald;Brazil,Russia andPakistan for aquamarine;California,Brazil,Africa, and many other localities for other beryls.
 * **Best Field Indicators** are crystal habit, lack of good cleavage, hardness and color.
 * **Color** is black to brown and yellow with weathering.
 * **Luster** is vitreous to pearly.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is monoclinic; 2/m
 * **Crystal Habits** include tabular to prismatic crystals with a prominant pinacoid termination. Biotite's four prism faces and two pinacoid faces form pseudo-hexagonal crystal "books". The sides of the crystal often tend to tapper and can have a "hard candy that has been sucked on, look". Also as lamellar or granular rock forming masses providing the luster for most schists and gneiss.
 * **Cleavage** is perfect in one direction producing thin sheets or flakes.
 * **Fracture** is not readily observed due to cleavage but is uneven.
 * **Hardness** is 2.5.
 * **Specific Gravity** is approximately 2.9 - 3.4+ (slightly above average)
 * **Streak** is white.
 * **Associated Minerals** are **[|quartz], [|feldspars], [|apatite], [|calcite], [|hornblende], [|garnets]** and **[|schorl]**.
 * **Other Characteristics:** cleavage sheets are flexible and elastic, meaning they can be bent and will flex back to original shape.
 * **Notable Occurrences** include Bancroft andsudbury,Ontario;Sicily;Russia and many other locallities around the world.
 * **Best Field Indicators** are crystal habit, color, cleavage, elastic sheets and associations.
 * **Color** is brown to black with a typical purplish-bluish tarnish, a reddish bronze color on freshly broken surfaces.
 * **Luster** is metallic.
 * **Transparency:**Crystals are opaque.
 * **Crystal System** is isometric; 4/m bar 3 2/m above 228 degrees celsius but below this temperature its structure becomes less symmetrical possibly tetragonal; bar 4 2/m.
 * **Crystal Habits** include rare distorted cubes and even more rarely dodecahedrons and octahedrons. Most common habit is massive or disseminated grains.
 * **Cleavage** is very poor, octahedral.
 * **Fracture** is conchoidal.
 * **Hardness** is 3
 * **Specific Gravity** is approximately 4.9 - 5.3 (average for metallic minerals)
 * **Streak** is a gray black.
 * **Other Characteristics:** The tarnish that occurs on fresh surfaces can form in only hours and will become black over time.
 * **Associated Minerals** are **[|magnetite], [|chalcocite], [|chalcopyrite], [|covellite], [|pyrrhotite], [|pyrite]** and other **sulfides**.
 * **Notable Occurances** include Bristol, Connecticut, Butte, Montana, Plumas Co., Colorado and Superior, Arizona, USA; Cornwall, England; Rhineland, Germany; Tsumeb, Namibia; South Africa; Morocco; Bolivia; Chile; Peru and Mexico.
 * **Best Field Indicators** are lack of good crystals, tarnish, streak, color of fresh surfaces and associations.
 * **Color** is extremely variable but generally white or colorless or with light shades of yellow, orange, blue, pink, red, brown, green, black and gray. Occasionally iridescent.
 * **Luster** is vitreous to resinous to dull in massive forms.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System** is trigonal; bar 3 2/m
 * **Crystal Habits** are extremely variable with almost any trigonal form possible. Common among calcite crystals are the scalenohedron, rhombohedron, hexagonal prism, and pinacoid. Combinations of these and over three hundred other forms can make a multitude of crystal shapes, but always trigonal or pseudo-hexagonal. **[|Twinning]** is often seen and results in crystals with blocky chevrons, right angled prisms, heart shapes or dipyramidal shapes. A notch in the middle of a doubly terminated scalenohedron is a sure sign of a twinned crystal. lamellar twinning also seen resulting in striated cleavage surfaces. Pseudomorphs after many minerals are known, but easily identified as calcite. Also massive, fibrous, concretionary, stalactitic, nodular, oolitic, stellate, dendritic, granular, layered, etc. etc.
 * **Cleavage** is perfect in three directions, forming rhombohedrons.
 * **Fracture** is conchoidal.
 * **Hardness** is 3 (only on the basal pinacoidal faces, calcite has a hardness of less than 2.5 and can be scratched by a fingernail).
 * **Specific Gravity** is approximately 2.7 (average)
 * **Streak** is white.
 * **Other Characteristics:** refractive indices of 1.49 and 1.66 causing a significant double refraction effect (when a clear crystal is placed on a single line, two lines can then be observed), effervesces easily with dilute acids and may be **[|fluorescent], [|phosphorescent], [|thermoluminescence]** and **[|triboluminescent].**
 * **Associated Minerals** are numerous but include these classic associations: **[|Fluorite], [|quartz], [|barite], [|sphalerite], [|galena], [|celestite], [|sulfur], [|gold], [|copper], [|emerald], [|apatite], [|biotite], [|zeolites],** several metal **[|sulfides],** other **[|carbonates]** and **[|borates]** and many other minerals.
 * **Notable Occurrences** include Pugh Quarry, Ohio; Rosiclare, Illinois; **[|Franklin, New Jersey]**; Elmwood, Tennessee; Brush Creek and other Missouri, Wisconsin, Kansas and Oklahoma localities, USA; Andreasburg, Harz Mountains and Saxony, Germany; Brazil; Guanajuato, **[|Mexico];** **Cornwall,** Durham and Lancashire, England; Bombay area of India; Eskifjord, Iceland; many African localities as well as others around the world with their own unique varieties.
 * **Best Field Indicators** are crystal habit, reaction to acid, abundance, hardness, double refraction and especially cleavage.
 * **Color** is usually blue but can also be colorless, yellow and tints of red, green and brown.
 * **Luster** is vitreous.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is orthorhombic; 2/m 2/m 2/m
 * **Crystal Habits** include the bladed crystals that are dominated by two large pinacoid faces top and bottom and small prism faces forming a jutting angle on every side. There are many variations of these faces but the flattened blades and tabular crystals are the most common. If the pinacoid faces become diminished or are absent, the resulting prismatic crystal has a rhombic cross section. This habit is rather common in specimens fromMadagascar. Also nodular, fibrous or granular.
 * **Cleavage** is perfect in one direction, less so in another direction.
 * **Fracture** is conchoidal.
 * **Hardness** is 3 - 3.5
 * **Specific Gravity** is approximately 3.9+ (above average for translucent minerals)
 * **Streak** is white.
 * **Associated Minerals** are **[|calcite], [|gypsum], [|strontianite], [|sulfur]** and **[|fluorite]**.
 * **Other Characteristics:** red color in flame test (see above), some specimens fluoresce under UV light.
 * **Notable Occurances** include Lake Erie region ofOhio,Michigan andNew YorkUSA;Madagascar;Sicily andGermany.
 * **Best Field Indicators** are crystal habit, color and flame test.
 * **Color** is brassy yellow, tarnishes to irredescent blues, greens, yellows and purples.
 * **Luster** is metallic.
 * **Transparency:**Crystals are opaque.
 * **Crystal System** is tetragonal; bar 4 2m
 * **Crystal Habits** are predominantly the disphenoid which is like two opposing wedges and resembles a tetrahedron.Crystals sometines twinned. Also commonly massive, and sometimes botryoidal.
 * **Cleavage** is rather poor in one direction.
 * **Fracture** is conchoidal and brittle.
 * **Hardness** is 3.5-4
 * **Specific Gravity** is approximately 4.2 (average for metallic minerals)
 * **Streak** is dark green.
 * **Other Characteristics:** Some striations on most crystal faces.
 * **Associated Minerals** are **[|quartz], [|fluorite], [|barite], [|dolomite], [|calcite], [|pentlandite], [|pyrite]** and other **sulfides**.
 * **Notable Occurances** includeChile,Peru,Mexico, Europe,South Africa, severalUSA sites and many others around the world.
 * **Best Field Indicators** are crystal habit, tarnish, softness and brittleness.
 * **Color** is copper colored with weathered specimens tarnished green.
 * **Luster** is metallic.
 * **Transparency** is opaque.
 * **Crystal System** is isometric; 4/m bar 3 2/m
 * **Crystal Habits** include massive, wires and arborescent or branching forms as the most common, whole individual crystals are extremely rare but when present are usually cubes and octahedrons. Occasionally, massive forms will show some recognizable crystal faces on outer surfaces.
 * **Cleavage** is absent.
 * **Fracture** is jagged.
 * **Streak** is reddish copper color.
 * **Hardness** is 2.5-3
 * **Specific Gravity** is 8.9+ (above average for metallic)
 * **Associated Minerals** are **[|silver], [|calcite], [|malachite]** and other secondary copper minerals.
 * **Other Characteristics:** ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices.
 * **Notable Occurrences** includeMichigan andArizona,USA;Germany;Russia andAustralia.
 * **Best Field Indicators** are color, ductility and crystal habit.
 * **Color** is highly variable. The color can be white or colorless, blue, red, yellow, green, brown, purple, and pink; there are also instance of color zonation.
 * **Luster** is vitreous to adamantine.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System** is trigonal; bar 3 2/m
 * **Crystal Habits** include sapphire's typical six-sided barrel shape that may taper into a pyramid, and ruby's hexagonal prisms and blades.
 * **Cleavage** is absent, although there is parting which occurs in three directions.
 * **Fracture** is conchoidal.
 * **Hardness** is 9
 * **Specific Gravity** is approximately 4.0+ (above average for translucent minerals)
 * **Streak** is white.
 * **Associated Minerals** include **[|calcite], [|zoisite], [|feldspars], [|micas]** and **[|garnets]**.
 * **Other Characteristics:** Refractive index is around 1.77; pleochroic (meaning color intensity is variable from different viewing directions); striations on parting surfaces.
 * **Notable Occurrences** includeBurma;Sri Lanka;North Carolina andMontana,USA; many African localities; several localities inIndia, and Middle Eastern and Southeast Asian countries.
 * **Best Field Indicators** are extreme hardness, density and crystal habit.
 * **Color** is variable and tends toward pale yellows, browns, grays, and also white, blue, black, reddish, greenish and colorless.
 * **Luster** is adamantine to waxy.
 * **Transparency** crystals are transparent to translucent in rough crystals.
 * **Crystal System** is isometric; 4/m bar 3 2/m
 * **Crystal Habits** include isometric forms such as cubes and octahedrons, twinning is also seen.
 * **Hardness** is 10
 * **Specific Gravity** is 3.5 (above average)
 * **Cleavage** is perfect in 4 directions forming octahedrons.
 * **Fracture** is conchoidal.
 * **Streak** is white.
 * **Associated Minerals** are limited to those found in **[|kimberlite rock]**, an ultramafic **[|igneous]** rock composed mostly of **[|olivine]**.
 * **Other Characteristics:** refractive index is 2.4 ( very high), dispersion is 0.044, fluorescent.
 * **Notable Occurrences** includeSouth Africa and other localities throughout Africa,India,Brazil,Russia,Australia, andArkansas.
 * **Best Field Indicator** is //extreme// hardness.
 * **Color** is often pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal.
 * **Luster** is pearly to vitreous to dull.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is trigonal; bar 3
 * **Crystal Habits** include saddle shaped rhombohedral twins and simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming. Never found in scalenohedrons.
 * **Cleavage** is perfect in three directions forming rhombohedrons.
 * **Fracture** is conchoidal.
 * **Hardness** is 3.5-4
 * **Specific Gravity** is 2.86 (average)
 * **Streak** is white.
 * **Other Characteristics:** Unlike calcite, effervesces weakly with __warm__ acid or when first powdered with cold HCl.
 * **Associated Minerals:** include **[|calcite], sulfide** ore minerals, **[|fluorite], [|barite], [|quartz]** and occasionally with **[|gold].**
 * **Notable Occurrences** include many localities throughout the world, but well known from sites in Midwestern quarries of the USA; Ontario, Canada; Switzerland; Pamplona, Spain and in Mexico.
 * **Best Field Indicators** are typical pink color, crystal habit, hardness, slow reaction to acid, density and luster.
 * **Color** is "pistachio" green to yellowish or brownish green, also brown to black.
 * **Luster** is vitreous.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** monoclinic; 2/m
 * **Crystal Habits** include long, somewhat prismatic or tabular crystals with a typically dominant pinacoid that the crystal is often flattened against. The terminations are wedge shaped or tappered pyramids. Many clusters show grooved slender crystals or acicular sprays. Also massive, fiberous or granular.
 * **Cleavage** good in one direction lengthwise.
 * **Fracture** is uneven to conchoidal.
 * **Hardness** is 6-7
 * **Specific Gravity** is 3.3-3.5
 * **Streak** white to gray
 * **Associated Minerals** **[|calcite], [|biotite], [|hornblende], [|actinolite], [|andradite garnet]** and other metamorphic minerals.
 * **Other Characteristics:** striated to the depth of grooves in some crystals.
 * **Notable Occurances**Untersulzbachtal,Austria;Italy;Baja,Mexico and many localities in theUSA.
 * **Best Field Indicators** only one direction of cleavage, crystal habit, color and hardness.
 * **Color** is off-white, yellow, or shades of red, orange to brown.
 * **Luster** is vitreous to dull if weathered.
 * **Transparency** crystals are usually opaque, may be translucent or rarely transparent.
 * **Crystal System** is monoclinic; 2/m
 * **Crystal Habits** include blocky or tabular crystals.Crystals have a nearly rectangular or square cross-section with slightly slanted dome and pinacoid terminations. Twinning is common. (see above). A psuedo-orthorhombic or psuedo-trigonal variety, found in alpine veins is called adularia, and forms more flattened tabular crystals.
 * **Cleavage** is good in 2 directions forming nearly right angled prisms.
 * **Fracture** is conchoidal or uneven
 * **Hardness** is 6
 * **Specific Gravity** is approximately 2.53 - 2.56 (average)
 * **Streak** is white.
 * **Associated Minerals** are **[|quartz], [|plagioclase feldspars], [|micas], garnets, [|tourmalines]** and **[|topaz]**.
 * **Other Characteristics:** some crystals may show opalescence and are called moonstone.
 * **Notable Occurrences** are many but these are a few of them:Salzburg,Austria;Cornwall,England andNew York,Vermont,Maine andNew Hampshire,USA.
 * **Best Field Indicators** color, lack of striations, cleavage, twinning if present and occurrence.
 * **Color** is extremely variable and many times can be an intense purple, blue, green or yellow; also colorless, reddish orange, pink, white and brown. A single crystal can be multi-colored.
 * **Luster** is vitreous.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System:** Isometric; 4/m bar 3 2/m
 * **Crystal Habits** include the typical cube and to a lesser extent, the octahedron as well as combinations of these two and other rarer isometric habits. Always with equant crystals; less common are crusts and botryoidal forms. **[|Twinning]** also produces penetration twins that look like two cubes grown together.
 * **Cleavage** is perfect in 4 directions forming octahedrons.
 * **Fracture** is irregular and brittle.
 * **Hardness** is 4
 * **Specific Gravity** is 3.1+ (average)
 * **Streak** is white.
 * **Other Characteristics:** Often **[|fluorescent]** blue or more rarely green, white, red or violet and may be **[|thermoluminescent], [|phosphorescent]** and **[|triboluminescent]**.
 * **Associated Minerals** are many and include **[|calcite], [|quartz], [|willemite], [|barite], [|witherite], [|apatite], [|chalcopyrite], [|galena], [|sphalerite], [|pyrite]** and other **sulfides**.
 * **Notable Occurrences** include in addition to those mentioned above Cumberland, England; Spain; China; Brazil; Morocco; Bancroft, Ontario, Canada; Naica, Chihuahua, **[|Mexico];** Germany; Elmwood, Tennessee; Rosiclare, Illinois; Fort Wayne, Indiana; Pugh Quarry and Wood County, Ohio; Nancy Hanks Mine, Colorado and many other USA localities as well as many other localities from around the world.
 * **Best Field Indicators** are crystal habit, color zoning, hardness (harder than calcite, but softer than quartz or apatite), fluorescence and especially the octahedral cleavage.
 * **Color** is extremely variable and many times can be an intense purple, blue, green or yellow; also colorless, reddish orange, pink, white and brown. A single crystal can be multi-colored.
 * **Luster** is vitreous.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System:** Isometric; 4/m bar 3 2/m
 * **Crystal Habits** include the typical cube and to a lesser extent, the octahedron as well as combinations of these two and other rarer isometric habits. Always with equant crystals; less common are crusts and botryoidal forms. **[|Twinning]** also produces penetration twins that look like two cubes grown together.
 * **Cleavage** is perfect in 4 directions forming octahedrons.
 * **Fracture** is irregular and brittle.
 * **Hardness** is 4
 * **Specific Gravity** is 3.1+ (average)
 * **Streak** is white.
 * **Other Characteristics:** Often **[|fluorescent]** blue or more rarely green, white, red or violet and may be **[|thermoluminescent], [|phosphorescent]** and **[|triboluminescent]**.
 * **Associated Minerals** are many and include **[|calcite], [|quartz], [|willemite], [|barite], [|witherite], [|apatite], [|chalcopyrite], [|galena], [|sphalerite], [|pyrite]** and other **sulfides**.
 * **Notable Occurrences** include in addition to those mentioned above Cumberland, England; Spain; China; Brazil; Morocco; Bancroft, Ontario, Canada; Naica, Chihuahua, **[|Mexico];** Germany; Elmwood, Tennessee; Rosiclare, Illinois; Fort Wayne, Indiana; Pugh Quarry and Wood County, Ohio; Nancy Hanks Mine, Colorado and many other USA localities as well as many other localities from around the world.
 * **Best Field Indicators** are crystal habit, color zoning, hardness (harder than calcite, but softer than quartz or apatite), fluorescence and especially the octahedral cleavage.
 * **Color** is yellow, brown, brownish red to black. Sometimes tarnished with irridescent colors.
 * **Luster** is earthy to dull for massive forms and metallic for crystals.
 * **Transparency** crystals are opaque.
 * **Crystal System** is orthorhombic; 2/m 2/m 2/m
 * **Crystal Habits** include prismatic and platy crystals, massive and aggregate forms include internally radiating or fibrous; reniform, botryoidal and stalactitic.
 * **Cleavage** is perfect in one direction.
 * **Fracture** is uneven to splintery.
 * **Hardness** is 5-5.5
 * **Specific Gravity** is variable at 3.3 to 4.3 (light for metallic minerals)
 * **Streak** is brown, brownish yellow to orange yellow.
 * **Associated Minerals** include a large list of minerals (particularly secondary deposit minerals).
 * **Notable Occurences** include many iron mines around the world; especially nice specimens come fromEngland,Mexico, and the Lake Superior region inMichigan,USA.
 * **Best Field Indicators** are crystal habit, streak and tarnish.
 * **Color** is golden "butter" yellow.
 * **Luster** is metallic.
 * **Transparency** is opaque.
 * **Crystal System** is isometric; 4/m bar 3 2/m
 * **Crystal Habits** include massive nuggets and disseminated grains. Also wires, dendritic and arborescent crystal clusters.
 * **Cleavage** is absent.
 * **Fracture** is jagged.
 * **Streak** is golden yellow.
 * **Hardness** is 2.5 - 3
 * **Specific Gravity** is 19.3+ (extremely heavy even for metallic minerals)
 * **Associated Minerals** include **[|quartz], [|nagyagite], [|calaverite], [|sylvanite], krennerite, [|pyrite]** and other **sulfides**.
 * **Other Characteristics:** ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices.
 * **Notable Occurrences** includeCalifornia andSouth Dakota,USA;Siberia,Russia;South Africa;Canada and other localities around the world.
 * **Best Field Indicators** are color, density, hardness, sectility, malleability and ductility.
 * **Color** is black silver.
 * **Luster** is metallic to dull.
 * **Transparency** crystals are opaque
 * **Crystal System** is hexagonal; 6/m 2/m 2/m
 * **Crystal Habits** include massive lamellar veins and earthy masses. also as scaly granules in metamorphic rocks.
 * **Hardness** is 1 - 2
 * **Specific Gravity** is 2.2 (well below average)
 * **Cleavage** is perfect in one direction.
 * **Fracture** is flaky.
 * **Streak** is black gray to brownish gray.
 * **Associated Minerals** include **[|quartz], [|calcite], [|micas], [|iron meteorites]** and [|tourmalines].
 * **Other Characteristics:** thin flakes are flexible but inelastic, mineral can leave black marks on hands and paper, weakly conducts electricity.
 * **Notable Occurrences** includeNew York andTexas,USA;Russia;Mexico; Greenland andIndia.
 * **Best Field Indicator** is softness, luster, density and streak.
 * **Color** is black silver.
 * **Luster** is metallic to dull.
 * **Transparency** crystals are opaque
 * **Crystal System** is hexagonal; 6/m 2/m 2/m
 * **Crystal Habits** include massive lamellar veins and earthy masses. also as scaly granules in metamorphic rocks.
 * **Hardness** is 1 - 2
 * **Specific Gravity** is 2.2 (well below average)
 * **Cleavage** is perfect in one direction.
 * **Fracture** is flaky.
 * **Streak** is black gray to brownish gray.
 * **Associated Minerals** include **[|quartz], [|calcite], [|micas], [|iron meteorites]** and [|tourmalines].
 * **Other Characteristics:** thin flakes are flexible but inelastic, mineral can leave black marks on hands and paper, weakly conducts electricity.
 * **Notable Occurrences** includeNew York andTexas,USA;Russia;Mexico; Greenland andIndia.
 * **Best Field Indicator** is softness, luster, density and streak.
 * "Selenite" is the colorless and transparent variety that shows a pearl like luster and has been described as having a moon like glow. The word selenite comes from the greek for Moon and means moon rock.
 * Another variety is a compact fiberous aggregate called "satin spar" . This variety has a very satin like look that gives a play of light up and down the fiberous crystals.
 * A fine grained massive material is called "alabaster" and is an ornamental stone used in fine carvings for centuries, even eons.
 * **Color** is usually white, colorless or gray, but can also be shades of red, brown and yellow.
 * **Luster** is vitreous to pearly especially on cleavage surfaces.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is monoclinic; 2/m
 * **Crystal Habits** include the tabular, bladed or blocky crystals with a slanted parallelogram outline. The pinacoid faces dominate with jutting prism faces on the edges of the tabular crystals. Long thin crystals show bends and some specimens bend into spirals called "Ram's Horn Selenite" Two types of twinning are common and one produces a "spear head twin" or "swallowtail twin" while the other type produces a "fishtail twin". Also massive, crusty, granular, earthy and fiberous.
 * **Cleavage** is good in one direction and distinct in two others..
 * **Fracture** is uneven but rarely seen.
 * **Hardness** is 2 and can be scratched by a fingernail.
 * **Specific Gravity** is approximately 2.3+ (light)
 * **Streak** is white.
 * **Associated Minerals** are **[|halite], [|calcite], [|sulfur], [|pyrite], [|borax]** and many others.
 * **Other Characteristics:** thin crystals are flexible but not elastic, meaning they can be bent but will not bend back on their own. Also some samples are fluorescent. Gypsum has a very low thermal conductivity (hence it's use in //drywall// as an insulating filler). A crystal of Gypsum will feel noticeably warmer than a like crystal of quartz.
 * **Notable Occurances** includeNaica,Mexico;Sicily;Utah andColorado,USA; and many other locallities throughout the world.
 * **Best Field Indicators** are crystal habit, flexible crystals, cleavage and hardness.
 * **Color** is clear or white but can be found blue, purple, pink, yellow and gray.
 * **Luster** is vitreous.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System** is isometric; 4/m bar 3 2/m
 * **Crystal Habits** are predominantly cubes and in massive sedimentary beds, but also granular, fibrous and compact. Some crystals show a crystal type called a hopper crystal discribed above.
 * **Cleavage** is perfect in three directions forming cubes.
 * **Fracture** is conchoidal.
 * **Hardness** is 2
 * **Specific Gravity** is 2.1+ (light)
 * **Streak** is white.
 * **Associated Minerals** include other evaporite deposit minerals such as several **sulfates, halides** and **[|borates]**.
 * **Other Characteristics:** Salty taste.
 * **Notable Occurrences** includeSearles Lake,California andUtah in theU.S.,Germany, andMulhouse,France.
 * **Best Field Indicators** are taste, cleavage and crystal habit.
 * //Hematite Rose// is a circular arrangment of bladed crystals giving the appearance of the flower of a rose.
 * //Tiger Iron// is a sedimentary deposit of approximately 2.2 billion years old that consists of alternating layers of silver gray hematite and red jasper, chert or even tiger eye quartz.
 * //Kidney Ore// is the massive botryoidal form and gives the appearance of lumpy kidney-like masses.
 * //Oolitic Hematite// is a sedimentary formation that has a reddish brown color and an earthy luster and is composed of small rounded grains.
 * //Specularite// is a micaceous or flaky stone that is sparkling silver gray and sometimes used as an ornamental stone.
 * **Color** is steel or silver gray to black in some forms and red to brown in earthy forms. Sometimes tarnished with iridescent colors when in a hydrated form (called Turgite).
 * **Luster** is metallic or dull in earthy and oolitic forms.
 * **Transparency:**Crystals are opaque.
 * **Crystal System** is trigonal; bar 3 2/m
 * **Crystal Habits** include tabular crystals of varying thickness sometimes twinned, micaceous (specular), botryoidal and massive. also earthy or oolitic.
 * **Cleavage** is absent. However, there is a parting on two planes.
 * **Fracture** is uneven.
 * **Hardness** is 5 - 6
 * **Specific Gravity** is 5.3 (slightly above average for metallic minerals)
 * **Streak** is blood red to brownish red for earthy forms.
 * **Associated Minerals** include jasper (a variety of **[|quartz]**) in [|banded iron formation]s (BIF or Tiger Iron), dipyramidal quartz, **[|rutile]**, and **[|pyrite]** among others.
 * **Notable Occurrences** especially nice specimens come fromEngland,Mexico,Brazil,Australia and theLake Superior region.
 * **Best Field Indicators** are crystal habit, streak and hardness.
 * **Color** is almost always black to dark green.
 * **Luster** is vitreous to dull.
 * **Transparency:**Crystals are generally opaque but thin crystals or exceptional specimens can be translucent.
 * **Crystal System** is Monoclinic; 2/m
 * **Crystal Habits** include short stocky prismatic crystals as well as long thin crystal forms.Crystals can have a hexagonal cross-section although rarely symmetrical. The typical termination, if seen, appears as the two faces of a dome but is actually two of the four faces of a prism. Also found granular, massive and occassionally acicular aggregates.
 * **Cleavage** is imperfect in two directions at 56 and 124 degrees.
 * **Fracture** is uneven.
 * **Hardness** is 5 - 6.
 * **Specific Gravity** is approximately 2.9 - 3.4 (somewhat above average for translucent minerals)
 * **Streak** is brown to gray.
 * **Other Characteristics:** pleochroic in translucent speciments. Large crystals have an almost striated or grainy appearance.
 * **Associated Minerals** are **[|quartz], [|feldspars], [|augite], [|magnetite], [|micas]** and many medium grade metamorphic minerals.
 * **Notable Occurrences** are numerous and includeBancroft,Ontario;Norway;Bohemia;Mt. Vesuvius,Italy andNew York,USA.
 * **Best Field Indicators** are crystal habit (especially cross-section), color and cleavage.
 * **Color** is usually white, colorless, greenish or yellow.
 * **Luster** is earthy.
 * **Transparency:**Crystals are translucent.
 * **Crystal System** is triclinic; ** 1 .**
 * **Crystal Habits** include foliated and earthy masses.Crystals of any size are quite rare, usually microscopic.
 * **Cleavage** is perfect in one direction, basal.
 * **Fracture** is earthy.
 * **Hardness** is ** 1.5 - 2 ** (can leave marks on paper).
 * **Specific Gravity** is ** 2.6 ** (average).
 * **Streak** is white.
 * **Other Characteristics:** Clay like properties when water is added.
 * **Associated Minerals** include **[|fluorite], [|microcline], [|pyrite], [|hemimorphite], [|augite], dickite, halloysite, [|montmorillonite], [|quartz], [|muscovite]** and other **[|clays].**
 * **Notable Occurrences** are spread around the world including the type locality of Kao-Ling, Jianxi, China as well as Cornwall and Devon, England; Haute-Vienne, France; Near Dresden, Saxony, Germany; Donets Basin, Ukraine; Huberdeau, Quebec, and near Walton, Nova Scotia, Canada and in the United States at Macon, Georgia; Dixie Clay Company Mine, South Carolina; near Webster, North Carolina; Arkansas; Mesa Alta, New Mexico and **[|Sterling Hill],** New Jersey.
 * **Best Field Indicators** are habit, softness, color, luster and clay like properties.
 * **Color** is usually white, colorless, greenish or yellow.
 * **Luster** is earthy.
 * **Transparency:**Crystals are translucent.
 * **Crystal System** is triclinic; ** 1 .**
 * **Crystal Habits** include foliated and earthy masses.Crystals of any size are quite rare, usually microscopic.
 * **Cleavage** is perfect in one direction, basal.
 * **Fracture** is earthy.
 * **Hardness** is ** 1.5 - 2 ** (can leave marks on paper).
 * **Specific Gravity** is ** 2.6 ** (average).
 * **Streak** is white.
 * **Other Characteristics:** Clay like properties when water is added.
 * **Associated Minerals** include **[|fluorite], [|microcline], [|pyrite], [|hemimorphite], [|augite], dickite, halloysite, [|montmorillonite], [|quartz], [|muscovite]** and other **[|clays].**
 * **Notable Occurrences** are spread around the world including the type locality of Kao-Ling, Jianxi, China as well as Cornwall and Devon, England; Haute-Vienne, France; Near Dresden, Saxony, Germany; Donets Basin, Ukraine; Huberdeau, Quebec, and near Walton, Nova Scotia, Canada and in the United States at Macon, Georgia; Dixie Clay Company Mine, South Carolina; near Webster, North Carolina; Arkansas; Mesa Alta, New Mexico and **[|Sterling Hill],** New Jersey.
 * **Best Field Indicators** are habit, softness, color, luster and clay like properties.
 * **Color** is black.
 * **Luster** is metallic to dull.
 * **Transparency:**Crystals are opaque.
 * **Crystal System** is isometric; 4/m bar 3 2/m
 * **Crystal Habits** are typically octahedrons but rarely rhombododecahedron and other isometric forms, most commonly found massive or granular. [|Twinning] of octahedrons into spinel law twins is seen occassionally.
 * **Cleavage** is absent although octahedral parting can be seen on some specimens.
 * **Fracture** is conchoidal.
 * **Hardness** is 5.5 - 6.5
 * **Specific Gravity** is 5.1+ (average for metallic minerals)
 * **Streak** is black.
 * **Associated Minerals** are **[|talc]** and **[|chlorite]** (schists), **[|pyrite]** and **[|hematite]**.
 * **Other Characteristics:** Magnetism stronger in massive examples than in crystals, striations on crystal faces (not always seen).
 * **Notable Occurrences** includeSouth Africa,Germany,Russia and many locallities in theUSA.
 * **Best Field Indicators** are magnetism, crystal habit and streak.
 * **Color** is banded light and dark green or (if crystalline), just dark green.
 * **Luster** is dull in massive forms and silky as crystals.
 * **Transparency** is opaque in massive form and translucent in crystalline forms.
 * **Crystal System** is monoclinic; ** 2/m .**
 * **Crystal Habits**in its massive forms are botryoidal, stalactitic or globular. Crystals are acicular or fibrous and form in tufts and encrustations. Frequently found as pseudomorphs of **[|azurite].**
 * **Cleavage** is good in one direction but rarely seen.
 * **Fracture** is conchoidal to splintery.
 * **Hardness** is ** 3.5-4 .**
 * **Specific Gravity** is ** 3.9+ ** (slightly heavy).
 * **Streak** is green.
 * **Other Characteristics:** Weakly effervesces in acid.
 * **Associated Minerals** include **[|limonite], [|chalcopyrite], [|bornite], [|native copper], [|calcite], [|cuprite], [|azurite], [|chrysocolla]** and many rare copper minerals such as **[|kolwezite], [|shattuckite], [|antlerite], [|brochantite], [|graemite], [|aurichalcite], [|sphaerocobaltite], [|atacamite], [|chalcophyllite], [|conichalcite], [|rosasite], [|chalcosiderite], [|clinoclase], [|cornetite], [|duftite], [|libethenite], [|liroconite], [|mixite]** and **[|mottramite]** among others.
 * **Notable Occurrences** include many classic mineral localities such as Shaba, Congo; Tsumeb, Nambia; Ural mountains, Russia; **[|Mexico];** several sites in Australia; England and several localities in the Southwestern United States especially in **[|Arizona],**USA.
 * **Best Field Indicators** are color banding, softness, associations and reaction to acid.
 * **Color** is white, silver, yellow, green and brown.
 * **Luster** is vitreous to pearly.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is monoclinic; 2/m
 * **Crystal Habits** include tabular crystals with a prominant pinacoid termination. Muscovites four prism faces form diamond shaped "books" and if modified by another pinacoid they form pseudo-hexagonal crystal "books". The sides of the crystal often tend to tapper. Also as lamellar rock forming masses and small flakes in detrital matterial. Twinned crystals can form flat five pointed stars.
 * **Cleavage** is perfect in one direction producing thin sheets or flakes.
 * **Fracture** is not readily observed due to cleavage but is uneven.
 * **Hardness** is 2 - 2.5.
 * **Specific Gravity** is approximately 2.8 (average)
 * **Streak** is white.
 * **Associated Minerals** are **[|quartz], [|feldspars], [|beryl]** and **[|tourmalines]**.
 * **Other Characteristics:** cleavage sheets are flexible and elastic, meaning they can be bent and will flex back to original shape.
 * **Notable Occurrences** includeIndia,Pakistan,Brazil and manyUSA locallities.
 * **Best Field Indicators** are crystal habit, cleavage, elastic sheets, color and associations.
 * **Color** is a light near emerald green to the more common pale yellowish green; also found colorless, greenish brown to black. A near colorless specimen is likely nearly pure forsterite, while a greenish-brown to black specimen may approach pure fayalite in composition. Anything in-between is olivine.
 * **Luster** is vitreous.
 * **Transparency:**Crystals are transparent to translucent.
 * **Crystal System** is orthorhombic; ** 2/m 2/m 2/m .**
 * **Crystal Habits** include flatten tabular to box shaped crystals, but good crystals are rare. More commonly found as grains in alluvial gravels and as granular xenoliths in magnesium rich volcanic rock. Also massive. **[|Twinning]** is rare, but has produced star shaped trillings.
 * **Cleavage** is poor in two directions at 90 degrees, is more distinct in fayalite.
 * **Fracture** is conchoidal.
 * **Hardness** is ** 6.5 - 7 .**
 * **Specific Gravity** is approximately ** 3.2 ** for **[|forsterite]** - ** 4.3 ** for **[|fayalite]** (above average for non-metallic minerals).
 * **Streak** is white.
 * **Other Characteristics:** Index of refraction is ** 1.64 - 1.70 ** and has double refraction.
 * **Associated Minerals** are **[|diopside], [|spinel], [|plagioclase feldspars], [|chromite], [|hornblende], [|serpentine], [|iron-nickel]** meteorites and **[|augite]**.
 * **Notable Occurrences** are numerous and include the ancient source of Zagbargad Island in the Red Sea off the coast of Egypt; Mogok, Myanmar (formerly known as Burma); South Africa; **Ural Mountains,** Russia; Kohistan, Pakistan; Norway; Sweden; France; Minas Gerais, Brazil; Eifel, Germany; Chihuahua, **[|Mexico];** Ethiopia; Victoria, Australia; China and Salt Lake Crater, Oahu, Hawaii; North Carolina; New Mexico and Peridot Mesa, San Carlos Apache Reservation, Gila County, **[|Arizona],** USA.
 * **Best Field Indicators** are color, hardness, mafic [|igneous] or metamorphic environment of formation, lack of good cleavage and density.
 * **Color** is white, colorless, pale yellow, pale red, gray or black when impurities are common. Diffraction can cause flashes of any color of the rainbow (play of light).
 * **Luster** is vitreous to pearly.
 * **Transparency:** Specimens are transparent to translucent (opalescent).
 * **Crystal System:** Does not apply because opal is **amorphous.**
 * **Habits** include massive, cavity-fillings such as in fractures and **[|geodes]**, nodular, reniform or as a replacement of other minerals and wood.
 * **Cleavage** is absent.
 * **Fracture** is conchoidal.
 * **Hardness** is **5.5 - 6**
 * **Specific Gravity** is approximately **2 - 2.5** (light)
 * **Streak** is white.
 * **Other Characteristics:** Most specimens will **[|fluoresce]** white or pale green, some **[|phosphoresce]** and all specimens can be very sensitive to impacts and low temperatures.
 * **Associated rocks** are chert (a form of microcrystalline **[|quartz]**), volcanic rocks and many others.
 * **Notable Occurrences** include many Western USA localities; **[|Mexico];**Australia;England;Czech Republic and many other localities around the world.
 * **Best Field Indicators** are color play & opalescence, low density, fluorescence, fracture filling tendency and lack of cleavage or crystal faces.
 * **Color** is brassy yellow.
 * **Luster** is metallic.
 * **Transparency:**Crystals are opaque.
 * **Crystal System** is isometric; bar 3 2/m
 * **Crystal Habits** include the cube, octahedron and pyritohedron (a dodecahedron with pentagonal faces) and crystals with combinations of these forms. Good interpenetration **[|twins]** called iron crosses are rare. Pyrite is commonly found in nodules. A flattened nodular variety called "//Pyrite Suns//" or "//Pyrite Dollars//" is popular in rock shops. Also massive or reniform and replaces other minerals and fossils forming pseudomorphs or copies.
 * **Cleavage** is very indistinct.
 * **Fracture** is conchoidal.
 * **Hardness** is 6 - 6.5
 * **Specific Gravity** is approximately 5.1+ (heavier than average for metallic minerals)
 * **Streak** is greenish black.
 * **Other Characteristics:** Brittle, striations on cubic faces caused by crossing of pyritohedron with cube. (note - striations on cube faces also demonstrate pyrite's lower symmetry). Pyrite (unlike gold) is not malleable.
 * **Associated Minerals** are **[|quartz], [|calcite], [|gold], [|sphalerite], [|galena], [|fluorite]** and many other minerals. Pyrite is so common it may be quicker to name the unassociated minerals.
 * **Notable Occurrences** includeIllinois andMissouri,USA;Peru;Germany;Russia;Spain; andSouth Africa among many others.
 * **Best Field Indicators** are crystal habit, hardness, streak, luster and brittleness.
 * **VARIETY OF: Crypto-crystalline [|Quartz], SiO**** 2 **
 * **USES: Gemstone and ornamental stone.**
 * **COLOR: black and/or white**
 * **HARDNESS: 7**
 * **CLEAVAGE: none**
 * **CRYSTAL** **SYSTEM: none visible (actual crystals are microscopic)**
 * **USES: Gemstone and ornamental stone.**
 * **COLOR: Nearly any color, even colorless. The key is the presence of banding**
 * **HARDNESS: 7**
 * **CLEAVAGE: none**
 * **CRYSTAL** **SYSTEM: none visible (actual crystals are microscopic)**
 * **Color** is as variable as the spectrum, but clear quartz is by far the most common color followed by white or cloudy (milky quartz). Purple (Amethyst), pink (Rose Quartz), gray or brown to black (Smoky Quartz) are also common. Cryptocrystalline varieties can be multicolored.
 * **Luster** is glassy to vitreous as crystals, while cryptocrystalline forms are usually waxy to dull but can be vitreous.
 * **Transparency:**Crystals are transparent to translucent, cryptocrystalline forms can be translucent or opaque.
 * **Crystal System** is trigonal; ** 3 2 .**
 * **Crystal Habits** are again widely variable but the most common habit is hexagonal prisms terminated with a six sided pyramid (actually two **[|rhombohedrons]**). Three of the six sides of the pyramid may dominate causing the pyramid to be or look three sided. Left and right handed crystals are possible and identifiable only if minor trigonal pyramidal faces are present. Druse forms (crystal lined rock with just the pyramids showing) are also common. Massive forms can be just about any type but common forms include botryoidal, globular, stalactitic, crusts of agate such as lining the interior of a geode and many many more.
 * **Cleavage** is very weak in three directions (rhombohedral).
 * **Fracture** is conchoidal.
 * **Hardness** is ** 7 ,** less in cryptocrystalline forms.
 * **Specific Gravity** is ** 2.65 ** or less if cryptocrystalline. (average)
 * **Streak** is white.
 * **Color** is typically pink to red or orange and even black.
 * **Luster** is vitreous to dull to pearly on polished surfaces.
 * **Transparency:**Crystals are generally translucent and rarely transparent.
 * **Crystal System** is triclinic; bar 1
 * **Crystal Habits** include crystals that have a blocky prismatic habit, however crystals are rare. More typically massive, coarse and fine granular aggregates.
 * **Cleavage** is perfect in two directions forming prisms with a rectangular cross-section.
 * **Fracture** is conchoidal.
 * **Hardness** is 5.5 - 6.5.
 * **Specific Gravity** is approximately 3.4 - 3.7+ (above average for translucent minerals)
 * **Streak** is white.
 * **Associated Minerals** are **[|calcite], [|pyrite], [|microcline], [|spessartine], pyroxmangite** and other manganese minerals.
 * **Other Characteristics:** May tarnish to a brown or black color upon exposure.
 * **Notable Occurrences** include Ural Mountains, Russia; Broken Hill, Australia; Langban, Sweden, Menas Gerais, Brazil and Massachusetts and Franklin, New Jersey, USA.
 * **Best Field Indicators** are color, black inclusions, lack of reaction to acid and hardness.
 * **Color** is silver white with exposed specimens tarnishing black.
 * **Luster** is metallic.
 * **Transparency** is opaque.
 * **Crystal System** is isometric; 4/m bar 3 2/m
 * **Crystal Habits** include massive and disseminated grains, wires and plates as the most common, whole individual crystals are extremely rare but when present are usually cubes, dodecahedrons and octahedrons. "Jack Frost" type crystal growth as shown on some specimens produces beautiful intricate structures. Wires can form coiled clusters that resemble rams horns.
 * **Cleavage** is absent.
 * **Fracture** is jagged.
 * **Streak** is silver white.
 * **Hardness** is 2.5-3.
 * **Specific Gravity** is variable according to purity 10-12 (well above average even for metallic minerals)
 * **Associated Minerals** are silver minerals such as **[|acanthite]** and **[|prousite], [|cobaltite], [|copper], [|zeolites]** and **[|quartz]**.
 * **Other Characteristics:** ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices.
 * **Notable Occurrences** includeMichigan andArizona,USA; Cobalt,Ontario;Chile; andGermany.
 * **Best Field Indicators** are color, tarnish, ductility and crystal habit.
 * **Color** is blue, white, gray, or even green.
 * **Luster** is vitreous or greasy
 * **Transparency:**Crystals are transparent to translucent, massive specimens are opaque.
 * **Crystal System:** Isometric; bar 4 3/m
 * **Crystal** **Habits:** Dodecahedral crystals have been found, usually massive as a rock forming mineral.
 * **Cleavage** is poor, in six directions, but rarely seen.
 * **Fracture** is uneven
 * **Hardness** is 5.5 - 6.0
 * **Specific Gravity** is 2.1 - 2.3
 * **Streak** white
 * **Associated Minerals** **[|calcite], [|nepheline], [|cancrinite]** and other **[|feldspathoids]**.
 * **Other Characteristics:** it is the only feldspathoid to give a positive chlorine test when dissolved in a HNO 2 dilute solution.
 * **Notable Occurrences** includeBancroft,Ontario;Mt. Vesuvius,Italy;Brazil;IceRiver area,British Columbia andMaine,USA.
 * **Best Field Indicators** are color if blue, lack of pyrite association (as in lazurite), hardness and associations.
 * **Color** is typically black but can be brown, yellow, reddish, green, and less commonly white or colorless.
 * **Luster** is adamantine or resinous or submetallic to earthy in massive forms.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is isometric; bar 4 3m
 * **Crystal Habits** can be complicated with the rhombic dodecahedron, tetrahedron and combinations of these having cubic and tristetrahedron faces giving the crystals multiple faces of often indistinct forms. To add more confusion to the indistinct crystals, **[|twinning]** is common and sometimes pervasive. Massive forms are common and can be granular, earthy, botryoidal, concretionary and fibrous. An aggregate of botryoidal crusts with layers of **[|wurtzite]** and **[|galena]** is called "Schalenblende" is sometimes cut and polished as an ornamental stone.
 * **Cleavage** is perfect in **six** directions forming dodecahedrons.
 * **Fracture** is conchoidal, but rarely seen because of frequent cleavage.
 * **Hardness** is 3.5-4
 * **Specific Gravity** is approximately 4.0 (heavier than average, but light when compared to most metallic minerals)
 * **Streak** is yellow to light brown (unusually light colored for a normally dark mineral).
 * **Other Characteristics:** Striations on tetrahedral faces, triboluminescent (meaning it may glow if crushed), an index of refraction of 2.37 - 2.42, a dispersion (fire) of 0.156 and finally sphalerite is pyroelectric (meaning that it forms a slight electrical charge when heated or cooled).
 * **Associated Minerals** almost always include **[|galena], [|pyrite], [|fluorite], [|chalcopyrite], [|quartz], [|calcite], [|magnetite], [|pyrrhotite]** and many others.
 * **Notable Occurrences** include Tri state area nearJoplin,Missouri;Rosiclare,Illinois;Elmwood,Tennessee,USA;Broken Hill,Australia;Italy;Spain;Burma;Peru;Morocco;Germany andEngland.
 * **Best Field Indicators** are crystal habits, streak, cleavage, high luster, softness and twinning.
 * **Color** is reddish-brown, brown, and black.
 * **Luster** is vitreous to resinous to dull.
 * **Transparency** crystals are translucent to opaque.
 * **Crystal System** monoclinic; 2/m
 * **Crystal** **Habits**: the typical crystal are prismatic or tabular. Some crystals can have a psuedo-hexagonal cross-section but most are flattened into a more diamond shaped cross-section with two of the four points truncated. [|Twinning] is seen in about 35% of the specimens encountered in nature. Twins are cross (+) or X-shaped and can be both at the same time.Crystals sometimes grown onto kyanite crystals.
 * **Cleavage** poor, in one direction.
 * **Fracture** is uneven to conchoidal
 * **Hardness** is 7-7.5
 * **Specific Gravity** is 3.7-3.8
 * **Streak** white
 * **Associated Minerals** include **[|almandine], [|micas], [|kyanite]** and other metamorphic minerals.
 * **Other Characteristics:**
 * **Notable Occurances**DucktownTennessee,Georgia,Virginia andMontana,USA;Brazil;Scotland,Italy andFrance.
 * **Best Field Indicators** are color, associations, twinning and crystal habit.
 * **Color** is a strong yellow color in thick crystals and duller yellow in small crystals to pale yellow in massive or powdery forms. Can also be reddish or greenish yellow with impurities.
 * **Luster** is vitreous to more often resinous or earthy in massive forms.
 * **Transparency** is transparent to translucent.
 * **Crystal System** is orthorhombic; 2/m 2/m 2/m
 * **Crystal Habits** include mostly massive or powdery forms but well shaped blocky crystals are common.Crystals can be made up of two dipyramids, one with steeper faces than the other, prisms and/or pinacoids in various combinations.
 * **Cleavage** is very poor in two directions.
 * **Fracture** is conchoidal.
 * **Streak** is yellow.
 * **Hardness** is 2.
 * **Specific Gravity** is 2.0 - 2.1 (well below average)
 * **Associated Minerals** are **[|celestite], [|calcite], [|aragonite]** and **[|gypsum]**.
 * **Other Characteristics:** odor (see above), poor heat conductivity makes it brittle when heated and can actually crack if held tightly in a person's hand.
 * **Notable Occurrences** includeMichigan andOhio,USA;Sicily;Poland andChile.
 * **Best Field Indicators** are color, odor, heat sensitivity, lack of good cleavage and crystal habit.
 * **Color** is green, gray and white to almost silver.
 * **Luster** is dull to pearly or greasy.
 * **Transparency** crystals are translucent and masses are opaque.
 * **Crystal System** is monoclinic; 2/m.
 * **Crystal** **Habits**: never in large individual crystals, but if found are flattened tabular crystals with a hexagonal cross-section, usually talc is found in compact or lamellar masses. Forms pseudomorphs (false shape) of other crystals such as **[|quartz], [|pyroxenes], [|olivine]** and **[|amphiboles]**.
 * **Cleavage** is perfect in one direction, basal.
 * **Fracture** is uneven to lamellar.
 * **Hardness** is 1 (can leave mark on paper)
 * **Specific Gravity** is 2.7 - 2.8 (average)
 * **Streak** is white.
 * **Other Characteristics:** cleavage flakes are slightly flexible but not elastic and talc has a soapy feel to the touch.
 * **Associated Minerals** include **[|serpentine], [|dolomite], [|magnesite], [|quartz], [|pyroxenes], [|olivine], [|biotite]** and **[|amphiboles]**.
 * **Notable Occurances:** include many mines up and down the Appalachian Mountains and inCalifornia andTexas,USA;Germany;Florence,Italy;Tyrol,Austria;Transvaal,South Africa andShetland,Scotland.
 * **Best Field Indicators** softness, color, soapy feel, luster and cleavage.
 * **Color** is clear, yellow, orange, red, blue and green.
 * **Luster** is adamantine to vitreous.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is orthorhombic; 2/m 2/m 2/m
 * **Crystal Habits** include a prismatic crystal with usually two different prisms that produce a rounded or sharp diamond-shaped cross-section. The termination is typically capped by a dome forming a roof like top. Another dome can modify the termination producing a point at the juncture of the two domes. A basal pinacoid can flatten the prisms termination or truncate the top of the domes. The pinacoid, multiple domes and occasionally orthorhombic pyramid faces can produce a complex, multifaceted and well formed termination. Topaz can be granular and massive.
 * **Cleavage** is perfect in one direction, basal.
 * **Fracture** is conchoidal.
 * **Hardness** is 8.
 * **Specific Gravity** is approximately 3.4 - 3.5+ (above average)
 * **Streak** is white.
 * **Associated Minerals** include **[|quartz], [|tourmalines], [|micas], [|brookite], [|cassiterite]** and **[|fluorite]**.
 * **Other Characteristics:** index of refraction is 1.61 - 1.64. Prism faces maybe striated lengthwise.
 * **Notable Occurrences** include Minas Gerias,Brazil;Pakistan; San Diego Co,California; Ural Mountains,Russia;Mexico and the Thomas Range, Utah.
 * **Best Field Indicators** are crystal habit, color, density and hardness.
 * **Color** is usually white or gray but can be greenish, colorless, yellow and violet.
 * **Luster** is vitreous or silky to dull.
 * **Transparency:** Specimens are translucent to transparent.
 * **Crystal System** is monoclinic; 2/m
 * **Crystal Habits** include flattened prismatic and elongated crystals with a dome-like termination that is actually two of the four faces of a prism. Fibrous crystals form radial aggregates, masses and hair like clusters. Also as a felted mass (asbestos and "mountain leather").
 * **Cleavage:** is perfect in two directions at close to 60- and 120-degree angles (diamond-shaped).
 * **Fracture** is uneven.
 * **Hardness** is 5 - 6.
 * **Specific Gravity** is approximately 2.9 - 3.1 (very slightly above average for translucent minerals).
 * **Streak** is white.
 * **Other Characteristics:** Index of refraction is 1.60 - 1.63.
 * **Associated Minerals** are **[|calcite], [|grossular], [|talc]** and **[|serpentine]**.
 * **Notable Occurrences** include the area around Wilberforce, Ontario, Canada; De Kalb, St Lawrence Co., New York, California, Arizona and Canaan, Connecticut, USA; Tyrol and Piemonte, Italy; Tremola Valley, Switzerland (hence the name); Tanzania and Finland.
 * **Best Field Indicators** are fibrosity (asbestos), color, cleavage, crystal habit and hardness.
 * **Color** is white or gray to colorless.
 * **Luster** is silky.
 * **Transparency** crystals are transparent to translucent.
 * **Crystal System** is triclinic; bar 1
 * **Crystal Habits** include tufts of acicular crystals called "cotton balls". Also as vein-like masses of parallel fibrous crystals.
 * **Cleavage** is perfect in one direction.
 * **Fracture** is fibrous.
 * **Hardness** is 2 (softer than a fingernail)
 * **Specific Gravity** is approximately 1.97 (very low density)
 * **Streak** is white.
 * **Associated Minerals** are **[|borax], [|colemanite], [|hydroboracite]** and other borate minerals.
 * **Other Characteristics:** similar borate minerals have an alkaline taste, while ulexite is tasteless.
 * **Notable Occurrences** include several localities inCalifornia andNevada,USA;Tarapaca,Chile andKazakhstan.
 * **Best Field Indicators** are crystal habit, associations, locality, density, unique optical property, and hardness.
 * ** Rock Type ** || ** Foliation ** ||  ** Hardness **  ||  ** Usual color **  ||  ** Grain size **  ||  ** Other **  ||
 * ** 60.)Gneiss ** || foliated || hard  ||  mix  ||  coarse  ||  banded  ||
 * ** 61.)Marble ** || Non-foliated || soft  ||  light  ||  coarse  ||   ||
 * ** 62.)Phyllite ** || foliated || soft  ||  dark  ||  fine  ||  Shiny; crinkly foliation  ||
 * ** 63.)Quartzite ** || Non-foliated || hard  ||  light  ||  coarse  ||  quartz  ||
 * ** 64.) Schist (Garnet) ** || foliated  ||  hard  ||  Mixed dark and light  ||  coarse  ||  Wrinkled foliation; often has large crystals  ||
 * ** 65.) Schist (Mica) ** || foliated  ||  hard  ||  Mixed dark and light  ||  coarse  ||  Wrinkled foliation; often has large crystals  ||
 * ** 66.) Slate ** || foliated  ||  soft  ||  dark  ||  fine  ||  “tink” when struck  ||
 * **Grain Size** || **Usual Color** || **Other** || **Composition** || **Rock Type** ||
 * fine || dark || glassy appearance || lava glass || **72.)Obisian** ||
 * fine || light || many small bubbles || lava froth from sticky lava || **74.)Pumice** ||
 * fine || dark || many large bubbles || lava froth from fluid lava || **76.)Scoria** ||
 * fine or mixed || medium || between felsite and basalt || medium-silica lava || **67.)Andesite** ||
 * fine or mixed || dark || has no quartz || low-silica lava || **68.)Basalt** ||
 * coarse || light || wide range of color and grain size || feldspar and quartz with minor mica, amphibole or pyroxene || **71.)Granite** ||
 * coarse || medium to dark || little or no quartz || low-calcium plagioclase and dark minerals || **69.)Diorite** ||
 * coarse || medium to dark || no quartz; may have olivine || high-calcium plagioclase and dark minerals || **70.)Gabbro** ||
 * very coarse || any color || usually in small intrusive bodies || typically granitic || **73.)Pegmatite** ||
 * Related to: Granite, pumice, **obsidian**
 * Color: White, gray, light black
 * Texture: Aphanitic(crystals too small to see) **to porphyritic** (a mixture of crystal sizes)
 * Origins: Volcanic arcs

** Sedimentary **  77. Anthracite Coal is usually considered to be the highest grade of coal and is actually considered to be metamorphic. Compared to other coals it is much harder, has a glassy luster, and is denser and blacker with few impurities. It is largely used for heating domestically as it burns with little smoke. 78. Arkose 79. Bituminous Coal is the coal most people are used to. The black, soft, slick rock is the most common coal used around the world. 80. Breccia 81. Chert is a **sedimentary** rock of biochemical origin. It is likely the result of the accumulation (in the deep ocean, far from land) of the silica shells of various micro-organisms such as diatoms. Note that the similar rock **chalk** is composed of the **calcite** shells of different micro-organisms. 82. Conglomerate 83. Coquina is a **sedimentary** rock of biochemical origin. It is formed when corals and seashells are consolidated into a rock. The component shells and corals retain much of their shape, and are generally poorly cemented. 84. Diatomite Diatomite, also known as diatomaceous earth, is the naturally occurring fossilized remains of diatoms. Diatoms are single-celled aquatic algae. They belong to the class of golden brown algae known as Bacillariophyceae. Diatomite is a near pure sedimentary deposit consisting almost entirely of silica. The Greeks first used diatomite over 2,000 years ago in pottery and brick. 85. Dolomite Rock or Dolostone is an evaporative sedimentary rock consisting primarily of the mineral **dolomite** (calcium magnesium carbonate). Since dolomite is less water soluble than **calcite**, it precipitates first and is also more stable when water containing magnesium penetrates a **limestone**, resulting in the gradual conversion of a limestone bed into a dolomite bed. 86. Lignite Coal (or brown coal) - is the least mature of the true coals and the most impure. It provides the least yield of energy of the true coals and burns the dirtiest. It is often crumbly, relatively moist and powdery. 87. Limestone [Chalk]  88. Limestone [Crystalline]  89. Limestone [Fossiliferous]  90. Limestone [Oolitic]  91. Limestone [Travertine] 87 to 91 - is a very common **sedimentary** rock of biochemical origin. It is composed mostly of the mineral **calcite**. Sometimes it is almost pure calcite, but most limestones are filled with lots of other minerals and sand and they are called dirty limestones. The calcite is derived mostly from the remains of organisms such as clams, brachiopods, bryozoa, crinoids and corals. These animals live on the bottom of the sea and when they die their shells accumulate into piles of shelly debris. This debris can then form beds of limestone. Some limestones may have been derived from non-biogenic calcite formation. Although some limestones can be nearly pure calcite, there is often a large amount or sand or silt that is included in the shelly debris. 92. Sandstone 93. Shale is a clastic **sedimentary** rock composed of silts, clays or muds that have been compacted into distinct layers. **Shales** may be easily split along these layers. Igneous Rocks  Born of Fire All Magma is made up of a fairly uniform mixture of elements. Some of the major elements present are silica, iron, sodium, potassium, aluminum, magnesium, and gasses including water vapor, oxygen, carbon dioxide, nitrogen, hydrogen and sulfur dioxide. These elements form chemical combinations that crystallize in patterns to form **eight basic rock forming minerals**. These eight minerals form most rock. They are **olivine, pyroxene, amphibole, orthoclase, plagioclase, muscovite, biotite, and quartz.** There are many kinds of volcanoes around the world. The materials that come from a volcano are different as well. We tend to lump them all under the term lava but rocks ranging from the very dense basalt to the very light pumice are just a part of what can come from a volcano. There is also ash, volcanic glass or obsidian, and the gem stone peridot to name a few. The molten magma can also crystalize below the surface. When the molten rock rises in the crust but cools before it reaches the surface it is **plutonic** igneous rock and is categorized as **intrusive**. The rate at which the magma cools determines the kind of rocks that are formed. Faster cooling surface lava creates rock that is fine grained or **aphanitic**. The rapid cooling doesn’t allow large crystals to form. I addition most of the gasses are driven off into the atmosphere. The slower cooling that takes place underground allows larger crystal formation. Granite is an example of this type of rock formation. Other igneous rocks are pumice, scoria, gabbro, basalt, ryolite, dacite, andesite and obsidian.All rocks begin as igneous rocks. Before rocks can be transformed by sedimentation and weathering or metamorphosed by the heat and pressure of plate tectonics they must first be cooled from the intense heat of the mantle. Whether they are formed from plutonic rocks deep within the crust of the earth or extruded onto the surface of the earth by volcanoes all rocks have a fiery beginning as igneous rocks. Metamorphic Rocks  Transformation at Work Metamorphic Rocks are rocks that have changed form due to **heat and pressure**. Metamorphic comes from the Greek words **meta** and **morph**. Meta means change and morph means form. So we get metamorphic meaning to change form. Metamorphic rocks were once sedimentary, igneous or even other metamorphic rocks that have been changed by heat and pressure. The heat and pressure comes from inside the earth. From the upper mantle up to within a few kilometers of the surface of the earth there is a tremendous amount of heat and pressure. This heat and pressure increase with depth. It is estimated that the temperature increases about 20o to 30o C per kilometer of depth. Foliated metamorphic rocks appeared banded or layered.Nonfoliated metamorphic rock usually contains one mineral. It is uniform in texture. Sedimentary Rocks  The Basics Each group forms in a very unique way by completely different processes. The word Sedimentary comes from the Latin word sedimentum, which means settling. All of the clastic rocks are formed from broken bits and pieces of other existing rocks that settle out of water or air. The broken bits and pieces are called sediments and are caused by weathering. Clastic sedimentary rocks are further organized according to the size of the sediment particles. There are three types of chemical sedimentary rocks: Another example of evaporate rocks can be found in your kitchen. Most table salt comes from Utah. The Great Salt Lake is the remnant of a vast inland sea that once covered much of the western United States. It is slowly shrinking in size due to evaporation. As the water evaporates the lake can no longer hold the same amount of salt. The salt precipitates out and is deposited as crystallized halite. This is the basic process for all evaporates. As water evaporates, the remaining water becomes saturated with elements. The water can no longer hold the elements in solution and they crystallize into solid form. Rocks are the record, set in stone, of how the earth formed. The clues are all around you. You just need to learn the language and soon you’ll be reading the pages of earth’s history in the rocks that surround you…anywhere you go!
 * **Hardness** || **Grain Size** || **Composition** || **Other** || **Rock Type** ||
 * hard || coarse || clean quartz || white to brown || Sandstone ||
 * hard || coarse || quartz and feldspar || usually very coarse || Arkose ||
 * hard or soft || mixed || mixed sediment with rock grains and clay || gray or dark and "dirty" || Wacke/ Graywacke ||
 * hard or soft || mixed || mixed rocks and sediment || round rocks in finer sediment matrix || Conglomerate ||
 * hard or soft || mixed || mixed rocks and sediment || sharp pieces in finer sediment matrix || Breccia ||
 * hard || fine || very fine sand; no clay || feels gritty on teeth || Siltstone ||
 * hard || fine || chalcedony || no fizzing with acid || Chert ||
 * soft || fine || clay minerals || splits in layers || Shale ||
 * soft || fine || carbon || black; burns with tarry smoke || Coal ||
 * soft || fine || calcite || fizzes with acid || Limestone ||
 * soft || coarse or fine || dolomite || no fizzing with acid unless powdered || Dolomite rock ||
 * soft || coarse || fossil shells || mostly pieces || Coquina ||
 * very soft || coarse || halite || salt taste || Rock Salt ||
 * very soft || coarse || gypsum || white, tan or pink || Rock Gypsum ||
 * __Sedimentary Rock Type:__ Biochemical
 * __Related to:__ Shale, sandstone and **limestone**
 * __Color:__ Generally black to dark brown or gray
 * __Texture:__ Amorphous and glassy to coarse fragments
 * __Origins:__ Swampy environments
 * Very hard
 * It's grain is very coarse
 * It's composition is quartz and feldspar
 * __Sedimentary Rock Type:__ Biochemical
 * __Related to:__ Shale, sandstone and **limestone**
 * __Color:__ Generally black to dark brown or gray
 * __Texture:__ Amorphous and glassy to coarse fragments
 * __Origins:__ Swampy environments
 * **__Sedimentary Rock Type:__ Clastic**
 * __Related to:__ Sandstoneand **conglomerate**
 * __Color:__ Variable
 * __Texture:__ Angular pebble to cobble sized grains sometimes in a finer grained matrix
 * __Origins:__ Debris flows, fault zones, **cryptolithic explosion events** and impact site deposits
 * **__Sedimentary Rock Type:__ Clastic**
 * __Related to:__ Sandstone and **breccias**
 * __Color:__ Variable
 * __Texture:__ Rounded pebble to cobble sized grains usually in a finer grained matrix
 * __Origins:__ River, ocean and glacier deposits
 * Coquina** is mostly **calcite**, although other shell forming minerals (such as **aragonite** or **apatite**) are also present.
 * __Sedimentary Rock Type:__ Biochemical
 * __Related to:__ Shale, sandstone and **limestone**
 * __Color:__ Generally black to dark brown or gray
 * __Texture:__ Amorphous and glassy to coarse fragments
 * __Origins:__ Swampy environments
 * __Sedimentary Rock Type:__ Clastic
 * __Related to:__ Shale, conglomerate, siltstone,**breccias**
 * __Color:__ highly variable
 * __Texture:__ Sand sized grains
 * __Origins:__ River, ocean, glacier and desert deposits
 * Shale** is a very common sedimentary rock, and often preserves fossils and sometimes even fossil tracks.
 * Igneous rocks ** get their name from the latin word for fire “igneus”. The name is appropriate because these rocks are born of fire. Beneath the thin rocky crust of the earth is the inferno of the mantle! The mantle is the origin of this rock type.
 * The Mantle ** Under the crust is the fiery hot mantle. Saying that the mantle is fiery hot does it injustice. The coolest outer part of the mantle is about 1000 degrees Celsius (1800 degrees Fahrenheit). Here the rock is molten liquid, white hot.
 * The Formation of Igneous Rock ** Igneous rocks are formed from this molten magma. These rocks form when the magma cools and crystallizes. This can happen above ground as with volcanoes it is then called **extrusive.**
 * How Cool ** When the magma reaches the surface it cools quickly, a matter of days or weeks.When the magma forms pockets underground it cools much more slowly. This could take thousands or even millions of years.
 * Metamorphic rocks ** are one of the three types of rock classifications, the other two being igneous and sedimentary. Rocks are classified by the processes under which they were formed. The differences in formation account for variations in the appearance of the rocks and, with some practice, you can learn to recognize the different types by sight.
 * There are two kinds of metamorphism. **
 * ** Contact metamorphism **
 * ** Regional metamorphism **
 * Contact metamorphism ** occurs when magma intrudes or forces its way into existing rock. The heat of the magma bakes the surrounding rocks causing them to change. This is a local event. The changes due to contact metamorphism are relatively small and are said to be low-grade metamorphism. An example of contact metamorphism is the metamorphic rock marble. Marble is created from limestone that has been subjected to heat.
 * Regional metamorphism ** by contrast takes place over large areas and is high-grade metamorphism. Regional metamorphism is associated with mountain building.
 * The Causes or Agents of Metamorphism ** The causes or **agents of metamorphism** are heat, pressure, and hydrothermal solution. But where does this heat and pressure come from? And what is hydrothermal solution? Well read on…
 * Plate Tectonics Adds Heat And Pressure ** There is something else that adds to both the heat and pressure, and that is plate tectonics. When the plates of the earth collide, they squeeze the rocks at the borders with unbelievable force. This force increases the pressure in this and surrounding areas. Friction is also created by the plates grinding together. This friction generates enough heat to melt the rocks at the point of contact.
 * Heat ** For metamorphism to occur **energy** is needed to fuel the chemical reactions. Heat is the primary source of this energy.
 * Pressure ** The pressure within the earth is the result of gravity pulling the crust of the earth downward. Like heat, pressure increases with depth. This pressure can actually squeeze the spaces out of the minerals within the rock. This makes the rocks denser. The heat and pressure together cause the rock to flow instead of break or fracture. The mineral grains become realigned. They flatten out and get longer.**Hydrothermal Solution**Magma contains many different gasses including H2O. That’s right water! Or more properly steam. Minerals are carried by the steam. When this hot fluid escapes from the magma it is called Hydrothermal Solution. These hot fluids can change the crystallization in rock by dissolving the minerals and then depositing new ones. Rocks that come in contact with this hydrothermal solution can have their composition altered as a result of this recrystalization.
 * The [|Classification of Metamorphic Rocks] ** Metamorphic rocks are classified as **foliated** or **nonfoliated.**
 * Sedimentary rocks ** are classified in three main groups: clastic, chemical, and organic.
 * Clastic Rocks ** < rock. of pieces and bits broken tiny are Sediments sediment. from formed rocks sedimentary>
 * Weathering ** All rocks are subject to weathering. Weathering is anything that breaks the rocks into smaller pieces or sediments. This can happen by the forces of wind, rain, or moving and freezing water.
 * Deposition ** The sediments that form from these actions are often carried to other places by the wind, running water and gravity. As these forces lose energy the sediments settle out of the air or water. As the settling takes place, the rock fragments are graded by size. The larger, heavier pieces settle out first. The smallest fragments travel farther and settle out last. This process of settling out is called deposition.
 * Erosion ** The combination of weathering and movement of the resulting sediments is called erosion.
 * Lithification ** Lithification is the changing of sediments into rock. There are two processes involved in this change. They are compaction and cementation.
 * Compaction ** occurs after the sediments have been deposited. The weight of the sediments squeezes the particles together. When more and more sediments are deposited on top, the weight on the sediments below increases. Waterborne sediments become so tightly squeezed together that most of the water is pushed out.
 * Cementation ** happens when dissolved minerals fill in the spaces between the sediment particles. These liquid minerals act as glue or cement to bind the sediments together.
 * Chemical sedimentary Rocks ** Chemical sedimentary rocks are not formed from sediments in the way that clastic sedimentary rocks are. Instead, they are formed from chemicals (elements) dissolved in water. Lakes, rivers, oceans, and ground water all have elemental chemicals dissolved in them.
 * Evaporites
 * 1) Halite or rock salt
 * 2) Gypsum
 * 3) travertine
 * Carbonates
 * 1) limestones
 * 2) dolostones
 * Siliceous rocks
 * 1) chert
 * Evaporates ** Evaporites form when bodies of water evaporate leaving behind deposits of one or more chemicals. Those white deposits on your sinks and faucets are the beginnings of this type of rock.
 * The Carbonates ** The carbonates are formed by chemical and biochemical processes. Limestones and dolostones are included in this group. They are made up primarily of two minerals, calcite CaCO3 and dolomite CaMg(CO3)2
 * Siliceous rocks ** The siliceous rocks are dominated by silica SiO2. Silica-secreting organisms like diatoms and radiolarians are responsible for the formation of this type of rock.
 * Organic sedimentary rocks ** Organic sedimentary rocks are composed of organic matter in the form of plant fragments. We usually think of this group of rocks as coal.
 * Lignite is black and has a crumbly consistency.
 * Bituminous coal can be dull to shiny and black.

The Rock Cycle  The Earth Recycles The Rock Cycle chart shows each type of rock connected by arrows. The arrows point from one rock form to a new form that it can become over time and exposure. Click on the picture if you want to learn more about that type of rock. For details on how rocks change from one form to another, click on the arrow. You’ll read about how rocks can change from one form to another. The Rock Cycle describes the process the earth uses to recycle rocks. Yes, even rocks are recycled. There are three basic types of rocks: [|igneous],[| metamorphic], and [|sedimentary]. The interesting part of knowing these names is that any one of the three types of rock can be changed into one of the other types. The names of the rock types refer to the way the rocks are formed. Igneous rocks are formed from fiery molten magma. Metamorphic rocks form under intense heat and pressure. Sedimentary rocks form by weathering.

Rocks continually change form. What started out as sedimentary rock may change to metamorphic and, with time and weathering, change back to sedimentary. What is a mineral? What is a mineral? These are the characteristics of minerals followed by a brief explanation of each characteristic. Let’s look at these one at a time. This is where it gets a little tricky. There are also marine animals that make their shells from calcite (calcium carbonate). Calcite is a mineral but since it is secreted by animals to form shells it is inorganic. Geologists generally consider this inorganic calcite a mineral. The vast majority of minerals are **compounds** or mixtures of elements. These mixtures are consistent. For halite, the chemical formula is NaCl or sodium chloride. Each sodium atom is combined with one chlorine atom. The formula for Quartz is SiO2, silicon oxide. For every atom of silicone, there are two atoms of oxygen. There are about 4000 known minerals on earth. Each one is a unique substance with its own chemical formula. Most of these are very rare. That narrows down the field quite a bit. There are only eight groups of minerals that are common. They are called **rock-forming minerals**. They are: Mineral Classification  The Dana System |||| Mineral Classification ** Crystal System Identification ** How can crystallography help an ordinary rockhound to identify minerals? A mineral's crystalline structure, the arrangement of its component atoms and/or ions, is responsible for the outward shape of the crystal (see crystal **[|habits]** and crystal **[|forms]).** Rarely does one mineral form crystals that are completely unique to itself. Rather, a mineral will form crystals that are consistent with the symmetry class that the mineral falls into, based on its own structure. Also, symmetry affects a number of other properties such as **[|cleavage], [|luster], [|hardness]** and at times **[|color].** Understanding what symmetry class a mineral belongs to is very helpful in identifying its crystals. There are several symmetry operations that help define the crystal's outward symmetry. These operations represent the way a crystal can repeat the facets or faces on their crystal's surface. One way to repeat a face is with a **mirror plane** that can reflect a face from one side of the crystal to the other. Consequent to being reflected by a mirror plane, the reflected face must be identical but reversed in orientation. In other words, if the original face has any right handed characteristics, then the reflected face must have the same characteristics but with a left handed slant to them. A **rotational axis** is a line imaginarily drawn through the crystal that acts as an axis just like the axis for a tire. A face can be repeated on a crystal when the crystal is rotated around this axis and a new face is left at various intervals during the rotation. Consequent to being rotated is that the face must be identical to the original face when the face is viewed head on. In other words, if the face has a right handed slant and is rotated, the rotated faces must keep the right handed slant. The interval for dropping a face is determined by a division of the full turn into equal segments. For example, to drop four faces on a crystal the rotation requires a stop at every 90 degrees and this type of rotation is called a four fold rotational axis. Rotational axes can have rotations of 1, 2, 3, 4 and 6 fold. Thus the 1 fold axis rotates the crystal in 360 degree intervals, the 2 fold interval is 180 degrees, the 3 fold interval is 120 degrees, the 4 fold interval is 90 degrees and the 6 fold interval is 60 degrees. A **rotoinversion axis** goes one step further, by after rotating once and before dropping a face, it inverts the face through the crystal's center to the other side. The resulting face is completely flipped, i.e., up is down and right is left. The rotoinversion continues until it returns to the original starting face. Rotoinversion is constrained by the same rules for the simple rotational axes with the same folds or turns and degrees. Finally a symmetry operation called a **center** is all that is left of symmetry operations to discuss. A center is simply, or perhaps not so simply, an operation that takes a face on one side of a crystal and inverts it through the center of the crystal. This has the same effect as the inversion in a rotoinversion operation in that the face is completely flipped up to down and right to left. Every point in a crystal is inverted to the other side of the crystal. Usually, a center is one operation that is all but ignored in most crystals because it is often caused by the juxtaposition of other symmetry operations. However in the triclinic system it is the only possible symmetry operation except for a one fold rotational axis, which is actually just returning a crystal face to its original position. Other axes mentioned are crystallographic axes that are used by crystallographers like geometric axes to plot the faces and symmetry elements and their orientations within the crystal. These axes may or may not be part of the symmetry of the crystals. But they usually are since crystallographers will often orient the crystallographic axes along the planes and axes of symmetry. Below is a list of links to the seven crystallographic systems and their member classes. Listed with the systems are the minimal requirements for a mineral to belong to that particular group. All crystalline solids can be classified as belonging to one of these systems based on its structure and inherent symmetry. Substances that are non-crystalline are called amorphous (without form) and are thus not classified. ** Other Identification Tips ** ** For Minerals ** Streak When a mineral is rubbed firmly across an unglazed tile of white porcelain (a streak plate), it leaves a line of powder. This is called the streak. The color of the streak is always the same, whether or not the mineral has impurities. For example, quartz leaves a white streak, whether it's violet (amethyst), pink (rose quartz), or brown (smoky quartz). Transparency Transparency describes how well light passes through a mineral sample. There are three degrees of transparency: transparent, translucent, and opaque. You can see objects through a transparent mineral. You can see light, but no objects through a translucent mineral. You can't see anything through an opaque mineral.
 * Let’s take a closer look at each type. **
 * Igneous Rocks ** Igneous rocks are formed of magma, the molten form of the earth’s mantle layer. Igneous rocks can form above ground as lava spewing from volcanoes. But igneous rocks can also form below the surface. Pockets of magma get stuck in layers of the earth. As they get closer and closer to the surface, the magma slowly cools. Granite is an igneous rock that formed from a slow-cooling pocket of magma.
 * Sedimentary Rocks ** Sedimentary rocks form from small weathered particles of other rocks or the weathered shells of sea animals. Wind and rain beating on the faces of exposed rock tend to wear off particles that are blown or washed to a new location. When sea creatures die, the shells settle on the bottom of the ocean. As the sediments pile up, they press together to form Sedimentary rock.
 * Metamorphic Rocks ** Metamorphic Rocks form under intense heat and pressure. Metamorphic rocks start out as igneous rocks, sedimentary rocks or other types of metamorphic rocks, but through heat or pressure, change characteristics such as sheen, tightness of grain and hardness.
 * A mineral: **
 * Is naturally occurring
 * Is a solid
 * Is inorganic (mostly)
 * Has a fixed chemical formula
 * Has an orderly crystalline structure
 * Naturally Occurring ** To be considered a mineral it must have been formed by natural geologic processes. Laboratory created gems (synthetic diamonds, rubies, etc.) don’t count.
 * A Solid ** By definition, minerals are solid within the normal temperature ranges of the earth’s surface.
 * Inorganic ** Generally, a mineral is a naturally occurring solid with a crystalline structure.
 * Halite ** or table salt is a mineral. **Sugar** is a crystalline solid but comes from plants, sugar cane or sugar beets. This classifies it as an organic compound and so is not a mineral. **Coal** on the other hand also comes from plants (organic) and is generally considered a mineral.
 * What is a mineral? It has a fixed chemical formula ** Each mineral has a particular chemical make up. While most minerals are compounds of two or more elements, some minerals are made up of a single element. Gold, silver and copper are called native elements and occur in nature in relatively pure form.
 * Native elements
 * Sulfides
 * Oxides
 * nitrates
 * phosphates
 * sulfates
 * Halides
 * Silicates
 * What is a mineral? It Has an orderly crystalline structure ** Minerals have an orderly crystalline structure. This means that the atoms or ions that make up a mineral are arranged in an orderly and repetitive manner.
 * Mineral classification ** can be an organizational nightmare. With over 3,000 different types of minerals a system is needed to make sense of them all. Mineralogists group minerals into families based on their chemical composition. There are different grouping systems in use but the Dana system is the most commonly used. This system was devised by Professor James Dana of Yale University way back in 1848. The Dana system divides minerals into eight basic classes. The classes are:
 * || **Native Elements** This is the category of the pure. Most minerals are made up of combinations of chemical elements. In this group a single element like the copper shown here are found in a naturally pure form. ||
 * || **Silicates** This is the largest group of minerals. Silicates are made from metals combined with silicon and oxygen. There are more silicates than all other minerals put together.The mica on the left is a member of this group. ||
 * || **Oxides** Oxides form from the combination of a metal with oxygen. This group ranges from dull ores like bauxite to gems like rubies and sapphires. The magnetite pictured to the left is a member of this group. ||
 * || **Sulfides** Sulfides are made of compounds of sulfur usually with a metal. They tend to be heavy and brittle. Several important metal ores come from this group like the pyrite pictured here that is an iron ore. ||
 * || **Slufates** are made of compounds of sulfur combined with metals and oxygen. It is a large group of minerals that tend to be soft, and translucent like this barite. ||
 * || **Halides** form from halogen elements like chlorine, bromine, fluorine, and iodine combined with metallic elements. They are very soft and easily dissolved in water. Halite is a well known example of this group. Its chemical formula is NaCl or sodium chloride commonly known as table salt. ||
 * || **Carbonates** are a group of minerals made of carbon, oxygen, and a metallic element. This calcite known as calcium carbonate is the most common of the carbonate group. ||
 * || **Phosphates** are not as common in occurrence as the other families of minerals. They are often formed when other minerals are broken down by weathering. They are often brightly colored. ||
 * || **Mineraloid** is the term used for those substances that do not fit neatly into one of these eight classes. Opal, jet, amber, and mother of pearl all belong to the mineraloids ||
 * Minerals usually form distinct crystals. ** The shape of the crystals has been found to play an important role in the identification of minerals. The study of crystals is called **//crystallography//** and is an important field of study. Not only do scientists in this field study natural crystals but also the crystals formed by metal alloys, chemicals, and other synthetic materials. Often it is the use of crystallographic tools, such as an x-ray spectrometer, that find and distinguish new minerals as well as verify or correct the identification of specimens. It is through the use of these tools that the structure of a crystal can be gleaned.
 * SYMMETRY OPERATIONS: **
 * CRYSTALLOGRAPHIC AXES: **
 * __ THESE ARE THE SEVEN CRYSTALLOGRAPHIC SYSTEMS: __**
 * **[|ISOMETRIC]**, requires 4 three fold axis of rotation.
 * **[|TETRAGONAL]**, requires 1 four fold axis of rotation.
 * **[|HEXAGONAL]**, requires 1 six fold axis of rotation.
 * **[|TRIGONAL]**, requires 1 three fold axis of rotation.
 * **[|ORTHORHOMBIC]**, requires either 3 two fold axis of rotation or 1 two fold axis of rotation and two mirror planes.
 * **[|MONOCLINIC]**, requires either 1 two fold axis of rotation or 1 mirror plane.
 * **[|TRICLINIC]**, requires either a center or only translational symmetry.
 * **AMORPHOUS**; no symmetry is present and it is therefore not a crystallographic system.

Luster Luster is the way the surface of a mineral reflects light. Luster should be observed on a cut or freshly broken, untarnished surface. There are two general types of luster -- metallic and non-metallic. The terms used to describe luster are:
 * * Metallic -- example: [|gold]
 * Vitreous (glassy) -- example: [|quartz], [|tourmaline]
 * Adamantine (brilliant) -- example: diamond
 * Resinous (like resin or sap from a tree) -- example: sphalerite
 * Greasy or waxy -- example: turquoise
 * Pearly -- example: talc
 * Silky -- example: asbestos
 * Dull or earthy -- example: bauxite ||

Hardness The hardness scale was established by the German mineralogist, Friedrich Mohs. The Mohs’ hardness scale places ten common or well-known minerals on a scale from one to ten. One is the softest mineral and ten is the hardest. These are the minerals used in the Mohs’ hardness scale: To use the hardness scale, try to scratch the surface of an unknown sample with a mineral or substance from the hardness scale (these are known samples). If the unknown sample cannot be scratched by feldspar (6) but it can be scratched by quartz (7), then it's hardness is between 6 and 7. An example of a mineral that has a hardness between 6 and 7 is [|pyrite] (6 to 6.5). If you don't have minerals from the hardness scale on hand, here are some common objects and their hardness values: |||||||||| ** Common Objects and Their Hardness Values ** If an unknown sample can not be scratched by your fingernail (2.5) but it can be scratched by a penny (3.5), then its hardness is between 2.5 and 3.5. An example of a mineral that has hardness between 2.5 and 3.5 is [|calcite] (3) Cleavage When a mineral sample is broken with a hammer, it breaks along planes of weakness that are part of its crystalline structure. These breaks are cleavages. Some minerals break only in one direction. Others break in two or more directions. Some common forms of cleavage are cubic, rhombohedral, and basal. Cubic cleavages form cubes (example, halite). Rhombohedral cleavages form six-sided prisms (example, [|calcite]). Basal cleavages occur along a single plane parallel to the base of the mineral (example, [|topaz]). If a mineral breaks easily and cleanly in one or more directions, its cleavage is considered perfect. For example, calcite cleaves perfectly along three planes. As the quality of the break decreases, cleavage may be described as good, distinct, and poor or none. Some minerals cleave perfectly in one direction and poorly in others. For example, [|gypsum] cleaves perfectly on one plane and poorly along two others. Fracture Not all minerals cleave easily. Some fracture instead. Unlike [|cleavages], which are usually clean, flat breaks, fractures can be smoothly curved, irregular, jagged or splintery. The most common types of fracture are conchoidal ([|quartz]), fibrous or splintery, hackly ([|copper]), uneven or irregular. Specific Gravity Specific gravity is the density of a mineral. Special equipment is usually needed to find out a mineral’s exact specific gravity. With a little practice, you can guess a mineral’s specific gravity by hand. Some mineral samples will feel heavier than others, even if all your samples are the same size. The heavier ones have a greater specific gravity. Here are some examples of common minerals and their specific gravity ranges:
 * ** Mohs' Hardness Scale ** ||
 * 1  ||   2   ||   3   ||   4   ||   5   ||   6   ||   7   ||   8   ||   9   ||   10   ||
 * Talc || Gypsum || Calcite || Fluorite || Apatite || Feldspar || Quartz || Topaz || Corundum || Diamond ||
 * 2.5  ||   3.5   ||   5.5   ||   6.5   ||   8.5   ||
 * Fingernail || Penny || Glass || Steel knife || Emery cloth ||
 * Fingernail || Penny || Glass || Steel knife || Emery cloth ||
 * ** Minerals ** ||  ** Density **  ||  ** Specific gravity **  ||
 * sulfur, graphite  ||   light   ||   1-2   ||
 * gypsum, quartz  ||   medium   ||   2-3   ||
 * fluorite, beryl  ||   medium heavy   ||   3-4   ||
 * corundum, most metal oxides  ||   heavy   ||   4-6   ||
 * native gold, platinum  ||   heaviest   ||   19   ||

Crystal Form Minerals grow in specific shapes, and usually crystallize into one of six crystal systems. The axes of the crystal, the angles at which the axes intersect, and the degree of symmetry define each system.
 * Isometric -- Also called the cubic crystal system. Crystalsare usually shaped like blocks, with similar and symmetrical faces. The crystal has three axes of symmetry, all at right angles to each other, and all of the same length.Example: [|pyrite].
 * Tetragonal -- Typically, the crystals are shaped like four-sided prisms and pyramids. Each crystal has three axes, all perpendicular to one another. Two axes are the same length and lie on a horizontal plane. The third axis is not the same length and is at a right angle to the other two.Example: zircon.
 * Hexagonal -- These crystals are usually shaped like six-sided prisms or pyramids. Each crystal has four axes of symmetry. Three lie in the same plane, are the same length, and intersect at 120° angles. The fourth axis is not the same length, and is perpendicular to other three.Example: [|beryl].
 * Orthorhombic -- These crystals are short and stubby. Each crystal has three unequal axes, all at right angles to one another.Example: [|topaz]
 * Monoclinic -- Crystalsare short and stubby with tilted faces at each end. Each crystal has three unequal axes. Two axes lie in the same plane at right angles to each other. The third axis is inclined.Example: [|gypsum].
 * Triclinic --Crystalsare usually flat with sharp edges, but exhibit no right angles. Each crystal has three unequal axes. None are perpendicular to one another. Example: feldspar