Notes :   - home || definitions || email || scioly
  - the Image URL is in relation to this page, which is http://www.scioly.org/rocks/
  - before printing, set orientation to "Landscape" and all margins to "0.3"
  - typos abound, most of them have been corrected (hopefully)

Rocks and Minerals is not a hard event, if you know the major characteristics of all the rocks, but it is very hard to memorize everything, so this chart is meant to help. But keep in mind, it is only meant to help; if you go into the event with nothing but the info on this page, you will not do well. This is because of the time limit you get at each station. My partner and I had barely enough time to read the questions and write the answers before time was called.
To really remember the rocks, I suggest getting a kit with the actual rocks in them, so you are exposed to the material itself and not only images. Another good thing to do is to do research on the rocks yourself, collecting different information off of different pages, and then reading it out loud to yourself. I'm not exactly sure why, but your brain is more likely to absorb the information this way (in my case, I did nothing but create this page in the process of preparing for the testing, and we placed third out of thirty-some schools). Also, though most of the event is to identify rocks, there are also several stations that just require basic knowledge, like how to check streak color or compare specific gravities.

Hardness table:

1: talc  6: feldspar6: window glass
2: gypsum2.5: fingernail7: quartz7: steel file
3: calcite3: copper penny8: topaz 
4: flourite 9: corundum 
5: apatite5.5: knife blade10: diamond 


Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Metamor.: Any rock that was formed in some fashion from a pre-existing rock, through heat, pressure, the effect of superheated fluids, or any combination of these forces.
Gneiss Can be made into Plaster of Paris and are used as building stones; the more mica in them, the less useful they are. Foliated Is formed by great heat and pressure (450 - 750 degrees C), so it's most likely formed inside the earth. Mostly contains feldspar, quartz, biorite, hornblende, and sometimes almandine, corundum, and staurolite. 2.7 - 2.9 quartz - feldspar: 6-7
micas: 2.5-3		 One rock may contain many layers of colors: gray, tan, pink, black, etc. Variable. Is banded, but with less than 50% of the softer minerals (mica, hornblende) in it (if >50%, is know as schist). Sometimes forms "eyes" with the banding, and then is known as augen gneiss. gneiss.html  
Marble Can be used for tiles, statues, and other ornaments. When crushed, it can be mixed in w/ concrete, roam metal, filter beds, etc. Dolomite-rich marble can be used in refracting materials. Foliated only when impure Contact or dynamothermal metamorphism of pure limestone or dolomite. Massive structure is common in contact, and dynamothermal creates more foliated marble. 2.56 3 White normally, black (carbons), green (diopside, hornblende, serpentine, or talc), red (hematite), yellow to brown (limonite), with dots or streaks Soft, glassy shine on fracture surface. Fine grained, smooth, even, occurs in regions of metamporphic rock with mica, schist and gneiss, or is next to intrusive igneous rocks. marble.html Calcitic marble DOES fizz; dolomitic marble will only fizz if acid is hot or rock is powder
Phyllite Quarried for roof slate, blackboards, flagstone, etc. It doesn't really have economic value. Foliated Dynathermal metamorphism under medium grade (250-450 degrees C) with more recrystallization than slate. 2.7 3 Medium to dark gray to black (from carbon and graphite). Sometimes green (chlorite), or red-purple-brown-yellow (iron oxides) Soft, silky sheen Foliation of mica flakes, and splits readily. Dense, with small crystals visible, and may contain porphyroblasts, like garnet. Usually jagged and irregular outcrops from erosion. phyllite.html  
Quartzite Is used for construction purposes. It is easy to carve and sculptures are made of it. In the Triassic age, it was known as "brownstone." Foliated or Extrusive Sedimen. There are two types: metaquartzite, a metamorphic rock through dynamotermal metamorphism through sandstone; and orthoquartzite, a sedimentary rock consisting of grains of silica sand cemented together by a least 10% of precipitated silica 2.65 > 6 Extremely varied, can be light colored when held together by calcite or quartz, and be brown to red to green as well. Grainy without much luster Is also known as sandstone. Quartz is the dominant mineral, and is held together by cementing rock. Is sometimes gritty. Layers of thin-bedded usually stand out over other sedimentary rocks that have less resistance to erosion. When the cementing material is quartz, then the sandstone is called quartzite. When broken, sandstone will become sand while quartzite will cleave. quartzite.html  
Schist Not very valuable, graphitic schist is used for graphite, and firmer ones are sometimes used for building. Foliated Dynamothermal metamorphism with temperature and pressure from low to high grade. 150 - 250 degrees C forms chlorite and albite. 250 - 450: garnet and epidote. 450 - 700: staurolite, kyanite, sillimanite. 2.7 mica: 6 - 7
garnet: 3.5 - 4		 Silvery white, grays, yellow and brown, depends on the color of the foliation mineral. Chemical weathering of biotite and limonite and such produce iron oxides, which give the yellow and brown colors. Fresh ones sparkle off cleavage surfaces. But luster dulls with time. Often in outcrops; coarse gained, and lots of mineral orientation. Foliation happens in thin plates or flakes and makes up 50% of the rock. Foliation if irregular and wavy, often forming eyes (augens). Garnet schist cleaves into rhombic dodecahedroms. schist.html  
Slate Quarried for roof slate, blackboards, flagstone, etc. It doesn't really have economic value. Foliated Dynathermal metamorphism under low-grade (150-250 degrees C) with less recrystallization than phyllite. 2.7 3 Medium to dark gray to black (from carbon and graphite). Sometimes green (chlorite), or red-purple-brown-yellow (iron oxides) Soft, silky sheen Foliation of mica flakes, and splits readily. Dense, with small crystals visible, and may contain porphyroblasts, like garnet. Usually jagged and irregular outcrops from erosion. slate.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Igneous: Rock formed by solidification of magma.
Andesite Little to none Extrusive Forms when dioritic magma erupts out as lava flows or when pushed into fractures of volcanic vents like dikes or domes. Occurs shallow-depth dike intrusions. 2.77 5 - 6 Brown, greenish, and dark gray Fairly dull Often porphyritic and can be easily confused with basalt when it's dark (the difference can only be noted at a microscopic level). Feldspar, amphibole, hornblende, pyroxene, and biotite must make an appearance. Accessories such as quartz, pyroxene, or feldspathoids. andesite.html  
Basalt Little to none Extrusive Forms when gabbroic magma erupts as lava flows or intrudes at shallow depths to form dikes and sills. Vesicular structure is prominent at the top of the lava flow. Then vesicles are formed by gasses trapped in the cooling lava. After solidification, secondary minerals like quartz and zeolites fill these cavities. 3.1 5 - 6 Dark gray to black; fresh basalt flows often have a dark-brown to reddish rusty color Fairly dull Anphanitic, but mostly porphyritic. Looks a lot like andesite. Really dark. Usually darker than andesite. Volcanic equivalent of plutonic gabbro and is rich in ferromagnesian minerals. Essential minerals: pyroxene, olivine, plagioclase feldspar. Accessory minerals: biotite, hornblende, magnetite, limonite, hematite, apatite, quartz. Secondary minerals: quartz, zeolites. basalt.html  
Diorite Good strength and durability and can take high polish. But isn't really used in architecture or ornamental stone because of it's "dark and unimpressive color." Intrusive Slow, deep-seated cooling and crystallization of magma richer in iron than the plutonic magma that creates granite. 3.37 5.5 - 6 Gray to dark gray, occasionally greenish or brownish gray. Quartz particles may reflect some light. Occurs as stocks, sills, and dikes. Similar to granite. Grayish silver (like the chat text) color with many black specks in it, like those rocks you find. Sometimes flow banded. Specks are feldspar or hornblende. diorite.html  
Gabbro Diabase (dolerite), a type of gabbro, is really strong because of it's interlaced crystal structure, and is widely used as crushed stone for concreted, road metal, railroad ballast, roofing granules, and riprap. It's commercial name is "trap rock." Less diabase are cut and polished for dimension stone ("black granite"). Instrusive By slow cooling and crystallization at depth in the earth's crust from a magma that is more fluid than granite magma. Olivine sinks to the bottom because of the fluid-ness, and thick layers of olivine form, along with other rock layers that crystallize later. 3 > 5.5 Dark gray, greenish black, rarely reddish. Sometimes lighter due to ferromagnesian (iron-magnetism). Normal - fairly dull Rather coarse-grained. Generally huge, but may show layered structure because of different minerals crystallizing. Distinct orbicular structure is sometimes shown. Sheetlike, saucer-shaped, lopoliths, or dikes and stocks. Weathers & erodes easily, so outcrops are small compared to granite. Olivine is an important mineral, usually on the bottom layer. gabbro.html  
Granite Because of its crushing strength, un-erode-ness, and high polish-able, widely used for architectural construction, ornamental stone, and monuments. Powdered, potash-rich ones are used in fertilizer. Instrusive Formed by the slow cooling and crystallization of magma at some depth in the earth's crust. Contains high amounts of silica, potassium, and sodium, but low in calcium, iron, and magnesium. 2.69 > 5.5 Depends on amount of feldspars. Usually white to gray or dark gray colors. Sometimes pink, peach, red to deep red (hematite). Normal to Fairly Dull Medium to coarse grained. Sometimes streaky by hornblende or gneisslike appearance. Block-jointed on large scale; 3 sets at right angles. Darkish speckles, looks like a pinkish version of diorite. granite.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Obsidian Primitive people valued obsidian highly. Made into knives, spearheads, and other implements w/ razor-sharp edges. Extrusive When silica-rich magma of granitic composition flows onto the surface and solidifies before minerals can develop and crystallize. Therefore is amorphous solid or glassy. 2.3 - 2.6 6 - 7 Generally black and may be smoky along translucent edges. Less often gray, reddish-brown, mahogany, dark green, etc. Black is sometimes mixed to produce marbled effect. Brilliantly vitreous; glassy Really oily/glassy texture. Black, glassy, lustrous and often flow-banded. Easily distinguished from other volcanic rocks. obsidian.html  
Pegmatite Pegmatite is a source of many important industrial minerals: feldspar, mica, spodumenen, lepidolite, beryl, and gem minerals like topaz, tourmaline, kunzite, etc. Extrusive Rapid crystallization of minerals from left-over fluids and gases from the cooling of granitic magma under high pressure. Under these conditions, well-formed, mineral crystals can form. 2.65 6 Very variable. Depends on amount of feldspars. Usually white to gray or dark gray colors. sometimes pink, peach, red to deep red (hematite). Reflective. Very course-grained and grain size and mineral distribution are highly variable. Is a lot like granite, but much more variable. Quartz, potash, feldspar, muscovite, and hornblende are essential minerals. Apatite, lepidolite, topaz, tourmaline, ect. are some of the accessory minerals. Sometimes can be largely banded, othertimes there are just specks of black in it. pegmatite.html  
Pumice Not very economical. Is a type of rhyolite. Extrusive Granitic magma erupts at the earth's surface or intrudes the crust at shallow depths. Since the lava cools quickly, only small crystals are able to form. 0.64 2 - 3 Shades of gray, yellow, brown, and pale to deep red. Shiny when the "fibers" catches light. Called "rock foam" or "volcanic foam" because of the many holes in it. It is so light it can float in water, and resembles a wooden sponge with really small vesicles. Partly glass as well. pumice.html  
Rhyolite Not very economical. Very similar to pumice. Extrusive Granitic magma erupts at the earth's surface or intrudes the crust at shallow depths. Since the lava cools quickly, only small crystals are able to form. 2.66 6 - 6.5 Shades of gray, yellow, brown, and pale to deep red. Glassy Partly glassy with small phenocrysts. Frequently shows pronounced flow banding. Pumice is a brittle variety of rhyolite. Is volcanic equivalent of plutonic granite, have more silica. Quite block-like, with banding or vesicles, and quite hard. rhyolite.html  
Scoria Little to none. Extrusive Forms when gabbroic magma erupts as lava flows or intrudes at shallow depths to form dikes and sills. Vesicular structure is prominent at the top of the lava flow. Then vesicles are formed by gasses trapped in the cooling lava. After solidification, secondary minerals like quartz and zeolites fill these cavities. 3.1 5 - 6 Dark gray to black; fresh basalt flows often have a dark-brown to reddish rusty color Fairly dull See basalt. Scoria usually has larger vesicles/holes. scoria.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Sedimen.: A layered rock, formed through the accumulation and solidification of sediments, which may originally be made up of minerals, rock debris, or animal or vegetable matter.
Anthracite Coal Coal is the most abundant and important fossil fuel of the world. However, antracite coal requires strong heat to ignite and has lower value than bituminous coal, but burns pale blue and w/o smoke smell. Anthracite is the most suitable for household, but is also the most expensive. Organic Formed by "destructive distillation of plant remains." It starts out as peat, which then becomes lignite (more solid and compact) (fixed carbon content = 25%). Then bituminous coal, from deeper in the earth, with fixed carbon content = 50-65%. Finally, antracite is arrived from that by temperatures and pressures deep. FCC = 85-95%. If higher pressures are contained, graphite or pure carbon will form. 1.51 2 - 2.5 Iron- to velvet- black Bright vitreous to submetallic Coal occurs in layers (miners call them seams) in thickness from 2.5 cm to about 3.6 m. Is a hard and black and lustrous form of coal. Contains a lot of carbon, with some hydrogen and oxygen along with sulfur and nitrogen. Breaks with pronounced conchoidal fracture. anthracite.html  
Arkose Can take polish and is sometimes used as ornamental stone or tiling. Clastic Disintegrations of granite and gneiss. The angular, fragmental nature of the grains serves to distinguish arkose from the closely interlocking igneous texture of granite. 2.32 4-5 Red, pink, or gray. Rusty Are known as feldspar-rich sandstones. Contains 25% or more of feldspar, rarely more than 50%; the rest is mainly quartz, but some biotite and muscovite may occur. The cement is usually calcite or iron oxides. arkose.html  
Bituminous Coal See anthracite coal. Occurs in greatest quantities of coal. Highest caloric value, but burns w/ yellow flame, and smoke smell. Organic See anthracite coal. (Located two rows above). 1.35 2 Iron- to velvet- black Dull Is a lot like anthracite coal, except with a lot less luster. Usually more brownish as well. Called "soft coal." Well jointed, breaking into rectangular pieces, often thinly laminated, tending to splintery or conchoidal fracture. Some fossil plants are visible also. bituminous.html  
Breccia Some tightly cemented breccia can become highly polished, and can be used as ornamental stone. Clastic Detrital, from coarse sediments. Are "pasted" together. Not rigors of turbulent or long-distance transport. 2.9 - 3.1 Highly variable Highly variable Variable A whole bunch of ANGULAR rocks pasted together by sticky, pasting material. Found after rock slides. breccia.html MIGHT fizz
Conglomerate Sometimes used for concrete aggregates. Clastic Detrital, from coarse sediments. Are "pasted" together. Have been tumbled, blah, traveled roughly and a lot, so the pebbles are rounded. 2.9 - 3.1 Highly variable Highly variable Variable A whole bunch of ROUNDED rocks pasted together by sticky, pasting material. Found in riverbeds. conglomerate.html MIGHT fizz
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Coquina Limestone widely used for interior & exterior architecture. Important ingredient in mortar and Portland cement, flux in iron- and steel-smelting. Dense limestone can be crushed for concrete aggregates and road metal. Clastically formed organic fragments Limestone mollusk shells and shell fragments cemented together poorly. Must contain a lot of silica (around 85-90%) 2.61 3-4 Pale-brown. Dusty Is a pale-brown, porous, poorly cemented organic limestone composed of marine or freshwater mollusk shells and shell fragments. coquina.html DOES fizz
Diatomite Diatomite is now used mostly as a filter aid; others like absorbent for industrial spills and as pet litter, a filler in paints and dry chemicals, insulation material, a mild abrasive in polishes, toothpaste, silica additive in cement. Organic The protists diatoms dying, leaving their pretty glassy shells behind, if enough of the shells gather and cement together, diatomite is formed. 2 (?) my: 0.75 Below 3 Light tan, cream, or white. Silky Extremely lightweight, lighter even than chalk. Called "fossil flour" because it easily falls apart into flour-like dust. Will float on water until saturated. Think of the protists diatoms w/ the shiny glassy shells that become diatomaceous earth when shed. Infact, diatomaceous earth is another name for diatomite. diatomite.html  
Dolomite Rock Many uses, like asphalt filler, concrete aggregate, riprap, roofing, flux in iron smelting, and source for metallic magnesium. Clastic / chemical ? Chemical sediments, most are formed by replacement of calcite in limestone by magnesium-rich water. Some other dolomite rock may form by direct precipitation from sea water on the ocean bottom, but geologists aren't sure. 2.83 - 2.9 3 - 4 Light gray, yellowish, pinkish, tan. Dull Dense, rarely even-granular. Similar to limestone. Not as much fossil variety as limestone, composed almost entirely of dolomite (has to have at least 50%). Easily weathered, commonly bedded w/ shale and sandstone. dolomite_rock.html Fizzes only when acid is hot or rock is powder
Lignite Can be burned as coal, does not work well. Organic Starts out as peat, which is an accumulation of partly decomposed plant stuff. Then it becomes lignite, a more solid material covered by sediments causing compaction of peat. 0.8 1 - 1.5 Generally chocolate brown, sometimes yellowish or black to velvet-black. Dull Soft/brown form of coal. Fixed carbon content: 25%. lignite.html  
Limestone [Chalk] See Coquina (located 4 lines above). Chalk is also board chalk. Organic Composed of shells of microscopic organisms and deposited in shallow marine water. 2.61 (?) my: 1 - 1.5 3 - 4 White Dusty Very similar to diatomite, only way to tell apart is that chalk reacts to hydrochloric acid. Most have no recognizable fossil remains. Think of board chalk. Is soft and porous, dense-textured. l_chalk.html DOES fizz
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Limestone [Crystalline]           Inclusions can be graphite, silicate minerals (e.g. serpentine, quartz, phlogopite, and feldspar).   Known as crystalline limestone it is really a coarsely crystalline calcite marble. Soft and has been eroded more deeply than other rocks. In many areas it is almost pure calcium carbonate. Although inclusions are very common.   DOES fizz
Limestone [Fossiliferous]               Limestone where fossils can still be seen.   DOES fizz
Limestone [Oolitic]               Oolitic limestone is a typical warm, shallow, sea-water deposit of limestone.   DOES fizz
Limestone [Travertine]               Travertine is a color-banded, crystalline deposit formed in caves and hot springs.   DOES fizz
Sandstone Principally used for construction. Greensands (glauconitic sandstones) have been used as a source of potash in fertilizer. Clastic Detrital, from sediments accumulated in a wide variety of environments such as beaches, deltas, floodplains, and deserts. 2.65 Variable Extremely varied, can be light colored when held together by calcite or quartz, and be brown to red to green as well. Grainy without much luster Is also known as sandstone. Quartz is the dominant mineral, and is held together by cementing rock. Is sometimes gritty. Layers of thin-bedded usually stand out over other sedimentary rocks that have less resistance to erosion. When the cementing material is quartz, then the sandstone is called quartzite. When broken, sandstone will become sand while quartzite will cleave. sandstone.html  
Shale Used in manufacturing of bricks, pottery, and other ceramics. Oil shales present fossil fuel. Clastic Detrital, from sediments deposited in the quiet environment of lake and ocean bottoms. 2.68 Easily scratched by knife. Normally light to dark gray, depending on the amount of organic debris present. May color buff, brown, reddish brown, or deep red. Muddy Dense with particles of silt and clay size. When mudstone is wet, it may break apart. Smooth, flat, and appears muddy. Generally massive w/ layers of several feet in thickness; shale is well laminated and tends to split into flat, shell-like fragments. Some may contain fossils. shale.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Minerals: The difference of minerals and rocks: minerals are the things that grow, while rocks are the environment in which minerals grow.
Albite [Plagioclase] Rarely used as gemstone. Tecto- silicate Name comes from Latin word albus, meaning white. Albite is the sodium-rich end member out of the Plagioclase Feldspar Group. Are important rock-forming minerals and are found in many kinds of igneous and metamorphic rocks. Can occur as bladed masses in granite pegmatites. 2.62 - 2.76 6 Streak = white. Can be white or colorless. Plagioclase Feldspars in general can be: white, colorless, gray, green, bluish, reddish, sometimes a play of colors in albite: blue, green, yellow, and red. Vitreous and frequently pearly on cleavage Mineral association and striations on cleavage surfaces that are too hard to be scratched w/ a knife. Twinning lamellae are narrower in soda-lime feldspars (like albite) than in lime-soda feldspars (labradorite, bytownite, and anorthite). albite.html  
Almandine [Garnet] Considered a gemstone. Neso- silicate Name comes from Alabanda, a town of ancient Caria. Some are of igneous origin, but most of them are products of metamorphism. Almandine occurs in diorite of plutonic rocks, and usually with andalusite, hornblende, and biotite in hornfels and schists of metamorphic rocks. (Fe3Al2Si3O12) 3.56 - 4.32 6.5 - 7.5 Streak = colorless. Deep red to brown, brownish black, purplish at times. Vitreous Crystal form is usually dodecahedron or trapezohedron. Fracture is conchoidal and uneven. Is brittle and transparent to opaque. almandine.html  
Amazonite [Microcline] Laminations and white streaks are not desirable. Good material is rare, but is used/polished into flats, beads, and cabochons. Tecto- silicate Is the potash feldspar that usually forms intergrowths with quartz and with albite in granite pegmatite. 2.5 - 2.6 6 - 6.5 Streak = white. Light, bluish-green Vitreous Amazonite is the light, bluish-green variety of microcline. Also called amazonstone. Perfect cleavage in two directions at 90 degrees. Twinned crystals very common. Transparent to translucent. Triclinic crystals. Lamination and white streaks common. amazonite.html  
Apatite Widely used in the manufacture of phosphate fertilizers. Gemstone. Phosphate Most common of all phosphorous-bearing minerals. Develops in many igneous rocks as a accessory mineral. Sometimes formed in metamorphic rocks. Occurs w/ titanite and magnetite in plutonic rocks; albite & muscovite in granite pegmatites; acmite and nepheline in nepheline syenite pegmatites; and andradite & phlogopite in hornfels of contact metamorphic rocks. 3.1 - 3.2 5 Streak = white. Green, brown, red, yellow, violet, pink, white, and colorless. Greasy vitreous Crystals are hexagonal, frequently tabular, very large (can be about 12" long). Coarse granular to compact. Cleavage is poor, one direction crosswise. Fracture is uneven and conchoidal. Brittle. apatite.html  
Aragonite Gemstone(?) Carbonate Occurs in evaporite deposits of chemical sedimentary rocks. Associated w/ gypsum, calcite, glaucophane, albite, lawsonite, azurite, chalcopyrite, and cuprite. 2.9 - 3.0 3.5 - 4 Streak = white. White, gray, colorless, yellow, pale green, violet, brown. Vitreous, resinous Prismatic cleavage and pseudohexagonal twin-crystal forms. Often twins many times, looks like little needle-like stabs coming out of the center (like a rigid kosh-ball). Sometimes can be twinned blobs. Cleavage is good in one direction, poor in two others. aragonite.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Augite No idea. Inosilicate Develops mainly in igneous rocks, sometimes an essential mineral. 3.2 - 3.6 5 - 6 Streak = greenish. Bright to dark green (usu. dark), grayish green, brown, black. Vitreous, submetallic (can be dull) Nearly right-angle cleavage and generally short, prismatic crystals. Crystals can be monoclinic, granular, or rarely fibrous as well. Fracture is uneven and brittle. The name comes from Greek word augites, which means brightness. augite.html  
Azurite Copper ore and minor ornamental stone. Carbonate Is a secondary copper mineral and develops in the zone of alteration in all types of hydrothermal replacement deposits. Often occurs w/ malachite, limonite, and chalcopyrite. 3.7 - 3.8 3.5 - 4 Streak = blue. Azure-blue, dark blue Vitreous or dull. Has an intense azure-blue color. Crystals are monoclinic, usually in well-formed equidimensional or tabular crystals. Has good, two-direction cleavage. azurite.html  
Bauxite Almost definitely not a gemstone. Is the principal ore of aluminum. Hydroxide Is a secondary material, usually formed at the surface by the alteration of minerals and rocks rich in aluminum. 2.4 - 2.6 1 - 3 Streak = white. White, gray, yellow, red, brown. Dull, grainy. Has no cleavage. Fracture is earthy. Crystals are massive to microcrystalline. Sometimes contains small, spherical brown masses. Pisolitic structure. bauxite.html  
Barite Used in oil-well drilling muds and in the manufacture of glass and paints. Sulfate Most common barium-bearing mineral. Occurs in carbonatites and massive hydrothermal replacement deposits. 4.3 - 4.6 3 - 3.5 Streak = white. White, gray, colorless, many shades of yellow, brown, red, blue. Vitreous, pearly. High density for a light-colored mineral. Can sometimes have "petals" and look like a rose. Crystals are orthorhombic, usually thin to thick tabular crystals. Also prismatic crystals, divergent groups, compact, lamellar, fibrous, and granular. Perfect cleavage in one direction, good in a second, and distinct in third. barite.html  
Beryl Gemstone (emerald, aquamarine, golden beryl, heliodor, morganite, goshenite are all versions of beryl). Also valuable industrially as a source of beryllium for use in alloy manufacturing. Cyclo- silicate Develops in pegmatites and some metamorphic rocks. Occurs w/ quartz, microcline, and muscovite in pegmatites; w/ quartz, muscovite, and almandine in schist of regional metamorphic rocks. 2.66 - 2.92 7.5 - 8 Streak = colorless. Bright green(emerald), blue, greenish blue(aquamarine), yellow (golden beryl), red, pink (morganite), white, colorless. Vitreous Six-sided outline and occurrence in pegmatites. Hexagonal crystals. Crystals are common, usually six-sided prisms that are striated lengthwise. Produces water-jewel looking gems. Cleavage is indistinct in one direction. beryl.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Biotite [Mica] No idea. Phyllo-silicate Common accessory mineral in plutonic, volcanic, and certain metamorphic rocks. Found in granite, dactite of volcanic rocks, contact metamorphic rocks, regional metamorphic rocks. 2.8 - 3.4 2.5 - 3 Streak = colorless. Black, brownish black, greenish black, dark green. Pearly, submetallic. Dark color and generally small crystals. Crystals are monoclinic, good crystals common, usually tabular, sometimes barrel-shaped; plates/scales. Thin plates tough, very elastic, becoming more brittle w/ alteration. Opaque to translucent. (note to self: remember the mica you saw in 3rd grade?) biotite.html  
Bornite Important copper-ore mineral Sulfide Common and widespread copper-sulfide mineral. Occurs in carbonatites, hydrothermal metamorphic rocks, mesothermal veins, missive, lode, and disseminated hydrothermal replacement deposits. 4.9 - 5.1 3 Streak = grayish black. Copper-red to bronze brown, tarnish deep blue, purple. Variegrated, metallic. No cleavage. Occurrence w/ other copper minerals and colorful tarnish (called peacock). Is gritty, but metallic looking. Crystals are isometric, they're rare but cubic, dodecahedral, rarely octahedral, compact, and granular. (note to self: think of that pyrite you have, now think diff. colors and smaller "grains") bornite.html  
Calcite Used in the manufacture of steel, cement, and glass. Carbonate Most common of all carbonate minerals and develops in nepheline syenite pegmatites, carbonatites, basalt of volcanic rocks, organic sedimentary rocks, contact metamorphic rocks, regional metamorphic rocks, hydrothermal metamorphic rocks, hypothermal / mesothermal / epithermal veins, and disseminated hydrothermal replacement deposits. 2.7 3 Streak = white. White colorless, pale shades of gray, yellow, red, green, blue, brown to black (impure). Vitreous or dull. Perfect cleavage in three directions, forming a rhombohedron. Double refraction (object image is doubled when viewed through crystal) in clear specimens. Crystals are hexagonal, commonly showing rhombohedron, scalenohedron, and prism; also tabular, acicular, cleavable, granular, compact, stalactic, oolitic, eary. Twinned crystals very common. calcite.html Fizzes VIGOROUSLY
Celestite Is used in the manufacture of caustic soda and special glasses. Sulfate Forms principally in evaporite deposits of chemical sedimentary rocks, usu. associated w/ halite & strontianite. 3.9 - 4 3 - 3.5 Streak = white. White, colorless, bluish, reddish. Vitreous, pearly. Light-blue color, which tints only part of a white or colorless crystal. Crystals are orthorhombic, usually thing to thick tabular crystals, also fibrous, nodular, rarely granular or lamellar. Cleavage is perfect in one direction, good in second, and distinct in third. Fracture is uneven. Brittle. Transparent to translucent, sometimes fluorescent. Can be quite large, even to 18". Small as well, 3.5". celestite.html  
Chalcopyrite Abundant and is important copper ore. Sulfide One of the most widely distributed copper minerals. Found in carbonatites, regional metamorphic rocks, hydrothermal metamorphic rocks, and in hypothermal / mesothermal veins. 4.1 - 4.3 3.5 - 4 Streak = greenish black. Brass-yellow, golden-yellow, tarnish or iridescent or deep blue, purple, black. Metallic Often occurs w/ some gold and silver. Fracture is uneven and brittle. Cleavage is poor in one direction. Crystals are tetragonal, commonly tetrahedral. Crystal faces usually uneven and some may contain striations in different direction. Often massive, compact, granular, and disseminated. Similar to pyrite, but pyrite is harder. Gold is not brittle, where chalcopyrite is. chalcopyrite.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Copper Native copper used as copper ore. Pennies/change. Pipes. Widely used. Uses are pretty well-known and obvious. Native element Develops in basalt of volcanic rocks by the reaction of copper-bearing solutions on the iron-oxide minerals in the basalt. Forms in disseminated hydrothermal replacement deposits also. 8.9 2.5 - 3 Streak = copper red. Copper-red, tarnish black, blue, green, orangish yellow. Shiny, metallic. Ductile and malleable. Copper color on fresh surface. No similar species. No cleavage. Fracture is hackly. Crystals are isometric, usually cubical and dodecahedral, rarely octahedral. Often flattened, elongated, distorted. Also scales, plates, lumps, and branching aggregates. (note: copper pennies...) copper.html  
Corundum Valuable gemstone. Blood-red corundum is called ruby. Other gem-quality is called sapphire, and may be pink, blue, green, violet, gray, yellow, or other colors. Can contain bundles of tube-like inclusions (star or catseye effect) in cut/polished stones. Rare orange variety is called padparadschah. Some are faceted, but most are worked into cabochons. Also used as an abrasive. Simple oxide Forms in nepheline syenite pegmatites, contact metamorphic rocks, and metamorphic terrains. 3.9 - 4.1 9 Streak = white. White, gray, brown to black, deep red, blue. Vitreous, adamantine. Striations on parting faces. Crystals are hexagonal, sometimes tapering prismatic. Pyramidal, tabular, often striated. Fracture is uneven, conchoidal. Transparent to translucent. Fluorescent. Brittle. No cleavage, although often conspicous parting in three directions. Can be up to 14". Everyone recognizes rubies, right? corundum.html  
Dolomite Used to make magnesia for industrial and medical use. Carbonate Develops in chemical sedimentary rocks, contact / regional metamorphic rocks, hypothermal / mesothermal / epithermal veins, and in disseminated hydrothermal replacement deposits. 2.8 - 2.9 3.5 - 4 Streak = white. White, colorless, pink, gray, green, brown, black. Vitreous, pearly. Curved faces and pearly luster. Crystals are hexagonal, commonly rhombohedral, w/ curved faces. Also granular, compact, and massive. Perfect cleavage in three directions. Unlike calcite, dolomite rarely fluoresces and has slightly higher density. Fracture is conchoidal, uneven. Transparent to translucent. Brittle. dolomite.html Will fizz if acid is hot or mineral is powder.
Epidote Occasionally gemstone. Soro- silicate Forms in granite pegmatites, basalt of volcanic rocks, contact metamorphic rocks, regional metamorphic rocks. 3.3 - 3.6 6 - 7 Streak = colorless or gray. Yellowish green to brownish black. Vitreous Cleavage is perfect in one direction lengthwise. Crystals are monoclinic, usually in long, slender, grooved prismatic crystals that are frequently terminated by two sloping faces. (note to self: this is what you would think if you thought tourmaline, but tourmaline has no cleavage while epidote does). epidote.html  
Feldspar [Orthoclase] Used as gemstones and in ceramics. Tecto- silicate Are important rock-forming minerals in plutonic, volcanic, and metamorphic rocks. See "amazonite," which is the light bluish-green variety of microcline (listed under orthoclase in field guide). 2.5 - 2.6 6 - 6.5 Streak = white. White, pink, brown, gray, green, colorless, yellowish. Vitreous Perfect cleavage in two directions at 90 degrees. Twinned crystals common. Plagioclase feldspars show twinning striations on fresh cleavage surfaces (I'm guessing orthoclase ones don't). Crystals are monoclinic, mostly single rectangular or square cross section and as tabular crystals. Fracture is uneven. feldspar.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Fluorite Gemstone. Used as a flux in the smelting of metallic ores. Is used in the manufacturing of steel and hydrofluoric acid. Halide Develops in several environments of widely different character. Such as contact metamorphic rocks, epithermal veins, and lode hydrothermal replacement deposits. 3.0 - 3.2 4 Streak = white. Violet, blue, green, yellow, brown, bluish black, pink, rose-red, colorless, white. Vitreous Cleavage is perfect in four directions, forming an octahedron. Crystals are isometric, usually cubic or as penetration twins. Less frequently octahedral and rarely dodecahedral. Fracture is uneven. Transparent to translucent. Brittle. Harder than calcite, and softer than quartz (those two are similar species). fluorite.html  
Galena Lead ore (most important). During the heyday of the crystal-detector radio receiver, galena was well known for its use as the crystal in the radio. Sulfide Most common of all lead minerals and occurs in skarn of hydrothermal metamorphic rocks, hypothermal / mesothermal veins, and mostly in lode and disseminated hydrothermal replacement deposits. 7.4 - 7.6 2.5 Streak = dark lead-gray. Dark lead-gray Metallic Perfect cleavage in three directions at 90 degrees, forming a cube. There isn't any other mineral like it, although sphalerite is similar, it lacks the cubic cleavage and lead-gray color. Crystals are isometric, commonly in cubes and combinations of cubes and octahedrons. Can be course or fine grained, fibrous. Fracture is subconchoidal (rarely), and brittle. galena.html  
Goethite Particularly in Europe, is an important iron ore. Hydroxide Secondary iron mineral and forms in the zone of alteration in al types of hydrothermal replacement deposits. Many materials formerly considered to be limonite are now id-ed as goethite. 3.3 - 4.3 5 - 5.5 Streak = yellow / yellowish brown. Yellow, yellowish brown, dark brown, black, or w/ multicolored tarnish. Submetallic, adamantine, dull Has a silky, fibrous structure, which limonite lacks. The streak is unique. Cleavage is perfect, one direction lengthwise. Fracture is uneven and splintery. Crystals are orthorhombic, small, black, shining prismatic, crystals are rare, commonly acicular, flattened plates, also compact, granular, foliated, earthy. goethite.html  
Graphite Used in lubricants and pencil "lead" Native Element Results from the metamorphism of carbonaceous material in sedimentary rocks and is therefore found in schists of regional metamorphic rocks and marble. 1.9 - 2.3 1 - 2 Streak = shiny gray to black Metallic, shining. Cleavage is perfect in one direction, thing flakes are flexible, sectile. Feels greasy. Crystals are hexagonal tablets, foliated, scaly, granular, and earthy. Easily confused w/ molybdenite, although graphite is lighter. (pencil lead...) graphite.html  
Gypsum [Alabaster] Used in artistic stone carving and ALL Gypsum is the main ingredient of Plaster of Paris. Sulfate Very common sulfate mineral. Principally found in chemical sedimentary rocks, forms gypsum deposits in beds up to 10m thick (that's the height of the eggdrop drop). Also in hydrothermal replacement deposits. 2.3 - 2.4 1.2 - 2 Streak = white. White, colorless, gray, yellow, red, brown. Vitreous, pearly on cleavage surfaces Massive, fine-grained variety of gypsum. Cleavage is perfect in one direction, distinct in two others. Crystals are monoclinic untwinned single crystals showing rhombic form common, may be twinned as arrowhead shape w/ beveled edges. Softer than muscovite, brucite, and calcite. Not as elastic as muscovite. Commonly occurs as flat, rhombic crystals. g_alabaster.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Gypsum [Satin-spar] Cut into cabochons because of its strong cats-eye effect. Sulfate Very common sulfate mineral. Principally found in chemical sedimentary rocks, forms gypsum deposits in beds up to 10m thick (that's the height of the eggdrop drop). Also in hydrothermal replacement deposits. 2.3 - 2.4 1.2 - 2 Streak = white. White, colorless, gray, yellow, red, brown. Vitreous, pearly on cleavage surfaces Fibrous form of Gypsum. Cleavage is perfect in one direction, distinct in two others. Crystals are monoclinic untwinned single crystals showing rhombic form common, may be twinned as arrowhead shape w/ beveled edges. Softer than muscovite, brucite, and calcite. Not as elastic as muscovite. Commonly occurs as flat, rhombic crystals. g_satinspar.html  
Gypsum [Selenite] Used as a flux for creating earthenware, and can be used as a fertilizer. Sulfate Very common sulfate mineral. Principally found in chemical sedimentary rocks, forms gypsum deposits in beds up to 10m thick (that's the height of the eggdrop drop). Also in hydrothermal replacement deposits. 2.3 - 2.4 1.2 - 2 Streak = white. White, colorless. Vitreous, pearly on cleavage surfaces Transparent, colorless variety. Comes from the Greek work selenites "moon stone." Cleavage is perfect in one direction, distinct in two others. Crystals are monoclinic untwinned single crystals showing rhombic form common, may be twinned as arrowhead shape w/ beveled edges. Softer than muscovite, brucite, and calcite. Not as elastic as muscovite. Commonly occurs as flat, rhombic crystals. g_selenite.html  
Halite Finds wide use in chemical industry as a source of chlorine and sodium. Halite IS salt. Halide Widespread in evaporite deposits of chemical sedimentary rocks. 2.16 2 - 2.5 Streak = white. Colorless; or w/ tints of gray, yellow, red, blue. Vitreous Salty taste (tasting is against the rules, but smelling is not. Salt has a distinct smell). Cleavage is perfect in three directions at 90 degrees (cube). Readily soluble in water. Faces are commonly cavernous and develop into "hopper" crystals. Fluorescent, brittle. Again, easily recognizable by salty smell. halite.html  
Hematite Principal iron ore. Simple Oxide Sedimentary origin. Also in igneous and metamorphic rocks. Occurs w/ quartz quite often. Occurs in carbonatites, contact and regional metamorphic rocks, mesothermal / epithermal veins, in lode and disseminated replacement deposits. 4.9 - 5.3 5 - 6 Streak = dark red, cherry-red, brownish red. Steel-gray, red, reddish brown, black. Metallic Red streak. No cleavage. Crystals are hexagonal, think to thing tabular, often as subparallel growth or as rosettes. Grape-like bulges at times. Coats other minerals such as calcite and quartz, other times alone. hematite.html  
Hornblende Resembled metal ores, but didn't produce very useful metals. Inosilicate Rock-forming mineral of some plutonic and metamorphic rocks. Essential mineral in granite, granodiorite, diorite, and monzonite. In balsalt of volcanic rocks, nepheline / syenite pegmatites, schists and gneisses of regional metamorphic rocks. 3.0 - 3.4 5 - 6 Streak = colorless. Green, brown, black. Submetallic, vitreous, pearly, silky. Cleavage angels of 56 and 124 degrees. Cleavages perfectly at two directions in the shape of a diamond. Fracture is uneven, splintery. Transparent to translucent on splinter edges. Brittle. Crystals are monoclinic, usually short to long prismatic crystals that have a diamond-shaped cross section. Granular, columnar, fibrous, radiated. Tourmaline lacks the good cleavage, tremolite and actinolite are lighter in color. hornblende.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Kaolinite Widely used as clay in pottery and ceramics, as a filler in paper products. Phyllo-silicate Secondary mineral, formed by the alteration, usually at shallow depth of aluminum silicates (generally feldspars) in soils and in rocks near the surface. 2.6 2 - 2.5 Streak = white. White, gray, yellowish. Dull. Pearly on cleavage. Friable claylike masses or plates. Cleavage is perfect in one direction. Fracture is earthy, plastic when wet. Brittle. Crystals are monoclinic, usually as submicroscopic grains or minute plates and in compact masses. kaolinite.html  
Lepidolite Used as a source o lithium Phyllo-silicate Confined to granite pegmatites, where it occurs either as fine-granular masses near the core or as stubby / tabular crystals in cavities. 2.8 - 2.9 2.5 - 3 Streak = colorless. Pink, lilac, yellowish, grayish white. Pearly Cleavage is perfect in one direction. Crystals are monoclinic, usually in scaly aggregates, rarely as well-developed crystals of sharp hexagonal outline, foliated, compact. Laminae, tough, elastic. Translucent to transparent. Hard to distinguish between pink lepidolite and pink muscovite. lepidolite.html  
Magnetite Some are naturally magnetized. Is an important iron ore. Multiple Oxide One of the most abundant and widespread of all oxide minerals. Occurs generally in igneous rocks and clastic sedimentary rocks. Contact metamorphic, regional metamorphic, hydrothermal metamorphic, massive / lode hydrothermal replacement deposits. 4.9 - 5.2 5.5 - 6.5 Streak = black. Iron-black Metallic Has no cleavage, although may have octahedral parting in four directions. Isometric crystals, usually octahedrons, sometimes dodecahedrons w/ striations. Massive, coarse or fine grained. Lamellar. Magnetized at times, and has a really dark streak. More magnetic than chromite and franklinte. Fracture is subconchoidal, uneven. Brittle. magnetite.html  
Malachite Copper ore & gemstone. Carbonate Secondary copper mineral develops in zone of alteration in massive / lode / disseminated hydrothermal replacement deposits. 3.9 - 4 3.5 - 4 Streak = light green. Emerald-green, grass-green, dark green. Adamantine, silky, dull. Green color and concentric color banding when massive. Cleavage is perfect one direction lengthwise. Fracture is conchoidal, splintery, translucent, brittle. Crystals are monoclinic, rare and usually short or long prismatic. Radial, fibrous, botryoidal, stalactitic, incrusting, earthy. malachite.html  
Muscovite [Mica] Thin transparent sheets (isinglass) used as windows in iron stoves. Filler in various industrial products. Insulator in electrical equip. Phyllo-silicate Common rock forming mineral. In granite pegmatites, contact metamorphic rocks, blue schist, schists / gneisses of metamorphic rocks, mesothermal veins. Almost all good specimens are found in granite pegmatites. 2.7 - 3.0 2 - 2.5 Streak = colorless. White, colorless, yellowish, greenish, pink, brownish, multicolored. Vitreous, pearly Very perfect cleavage in one direction, into think, flexible, elastic flakes and tapering of the prism faces. Translucent to transparent. Crystals are monoclinic, commonly tabular parallel to the cleavage, often hexagonal in outline. Foliated. (shiny/lightcolored mica). muscovite.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Olivine Gemstone (Peridot) Dark yellow-ish green are most valuable. Called "evening emerald" because it looks like an emerald at night. Neso- silicate Rock-forming mineral. Occurs as an essential mineral in gabbro, peridotite, and basalt. 3.2 - 4.3 6.5 - 7 Streak = colorless. Yellowish green, yellowish brown, reddish. Vitreous Crystals are orthorhombic, rare, usually in rounded grains, granular masses. Cleavage is indistinct in two directions at 90 degrees. Fracture is conchoidal, uneven. Transparent to translucent. Brittle. Apatite is softer and is fluorescent. Green tourmaline is not found in volcanic rocks or gabbros, and green garnet lacks cleavage. olivine.html  
Opal Gemstone. Dark body color and many colors are called black opal. Light body color and many colors are white opal. Transparent to translucent opal w/ orange-yellow to red is fire opal. Black opal is most highly prized. Most are cabochons, but some fire opals are faceted. Tecto- silicate Low-temperature mineral and usually develops in wide variety of rocks as cavity and fracture fillings. Frequently amygdules in basalt and rhyolite of volcanic rock. Replaces cells in wood and shells of clams. 2 - 2.2 5.5 - 6.5 Streak = white. White, yellow, red, pink, brown, green, gray, blue, colorless. Frequently shows rich internal play of colors. Vitreous, pearly. Easily recognizable by opalescence. Conchoidal fracture. Dense opal resembles quartz, but opal is softer. No crystals, usually massive. Botryoidal, reniform, stalactitic, earthy. No cleavage. opal.html  
Pyrite "Fools gold" Can be important gold ore. Commercial importance as source of sulfur. Used in manufacture of sulfuric acid; iron maybe be produced as by-product. Sulfide Most widespread and abundant of sulfide. Occurs in all types of hydrothermal veins, granite pegmatites, syenite pegmatites, carbonatites, regional metamorphic rocks, skarn of hydrothermal metamorphic rocks, mesothermal / epithermal veins, lode and disseminated hydrothermal replacement deposits. 4.9 - 5.2 6 - 6.5 Streak = greenish black. Pale yellow to brass-yellow. Tarnished w/ brownfilm of iron oxide. Becomes more silvery-yellow after a while. Sometimes iridescent, metallic. No cleavage. Fracture is uneven, brittle. Striations on crystal surfaces. Crystals are isometric, mostly in cubes and pyritohedrons w/ parallel striations on faces, less commonly in octahedrons. Also in nodules and massive forms. Fine to coarse granular, fibrous, mammillary, stalactitic. (note to self: you have one) pyrite.html  
Quartz [Agate/Onyx] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Formed generally near the earth surface where temperatures and pressures are relatively low. Forms in the zone of alteration of lode and massive hydrothermal replacement deposits. 2.6 - 2.64 7 Streak = white. Variegated, banded (agate). sard and carnelian (clear red to brownish red) in layers (sardonyx and onyx) Waxy, vitreous, dull. No crystals. Sometimes weakly fluorescent. Brittle to tough. Transparent to translucent. Distinctly banded where adjacent bands differ in color and in degree of translucency (note to self: you have one). q_agate.html  
Quartz [Amethyst] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Is an important rock-forming mineral. Is a constituent of granite, sandstone, contact metamorphic rocks like gneiss, schist, etc. In hypothermal / mesothermal / epithermal veins. In most lode / disseminated hydrothermal replacement deposits. 2.65 7 Streak = white. Purple. Vitreous, greasy. Violet to red-purple quartz is called amethyst. Generally no cleavage, rarely indistinct rhombohedral parting. fracture is conchoidal, transparent to subtranslucent. Crystals are hexagonal, usu. prismatic crystals striated crosswise and ended like hexagonal pyramids. (note to self: you have a small one). q_amethyst.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Quartz [Chalcedony] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Formed generally near the earth surface where temperatures and pressures are relatively low. Forms in the zone of alteration of lode and massive hydrothermal replacement deposits. 2.6 - 2.64 7 Streak = white. White to gray, brown, blue, black. Waxy, vitreous, dull. Chalcedony is the microcrystalline variety of quartz. Its crystals usually occur as crusts showing botryoidal and mamillary forms. Has no cleavage. Fracture is conchoidal, transparent to translucent. Sometimes weakly fluorescent. Brittle to tough. Often formed w/ a few bulged parts, although like a 3D parallelogram at times also. see varieties: agate/onyx, chert/flint, jasper  
Quartz [Chert/Flint] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Formed generally near the earth surface where temperatures and pressures are relatively low. Forms in the zone of alteration of lode and massive hydrothermal replacement deposits. 2.6 - 2.64 7 Streak = white. Whitish, dull gray, smoky brown to black. Waxy, vitreous, dull. Its crystals usually occur as crusts showing botryoidal and mamillary forms. Has no cleavage. Fracture is conchoidal, transparent to translucent. Sometimes weakly fluorescent. Brittle to tough. q_chert.html  
Quartz [Citrine] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Is an important rock-forming mineral. Is a constituent of granite, sandstone, contact metamorphic rocks like gneiss, schist, etc. In hypothermal / mesothermal / epithermal veins. In most lode / disseminated hydrothermal replacement deposits. 2.65 7 Streak = white. Clear yellow, red-orange, orange-brown. Vitreous, greasy. Yellow to red-orange or orange-brown quartz is called citrine. Generally no cleavage, rarely indistinct rhombohedral parting. fracture is conchoidal, transparent to subtranslucent. Crystals are hexagonal, usu. prismatic crystals striated crosswise and ended like hexagonal pyramids. q_citrine.html  
Quartz [Crystal] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Is an important rock-forming mineral. Is a constituent of granite, sandstone, contact metamorphic rocks like gneiss, schist, etc. In hypothermal / mesothermal / epithermal veins. In most lode / disseminated hydrothermal replacement deposits. 2.65 7 Streak = white. Colorless, transparent. Vitreous, greasy. The most common type of quartz, which is transparent is known as rock crystal quartz. Generally no cleavage, rarely indistinct rhombohedral parting. fracture is conchoidal, transparent to subtranslucent. Crystals are hexagonal, usu. prismatic crystals striated crosswise and ended like hexagonal pyramids. q_crystal.html  
Quartz [Jasper] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Formed generally near the earth surface where temperatures and pressures are relatively low. Forms in the zone of alteration of lode and massive hydrothermal replacement deposits. 2.6 - 2.64 7 Streak = white. Variegated and mottled red, yellow, brown. Waxy, vitreous, dull. Mottled yellow, red, brown, or green chalcedony is called Jasper. Its crystals usually occur as crusts showing botryoidal and mamillary forms. Has no cleavage. Fracture is conchoidal, transparent to translucent. Sometimes weakly fluorescent. Brittle to tough. q_jasper.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Quartz [Milky] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Is an important rock-forming mineral. Is a constituent of granite, sandstone, contact metamorphic rocks like gneiss, schist, etc. In hypothermal / mesothermal / epithermal veins. In most lode / disseminated hydrothermal replacement deposits. 2.65 7 Streak = white. Milk-white. Like the whitish rocks used to bed trees. Vitreous, greasy. It's the thing that looks like crystal quartz, but is white, rather than colorless. Generally no cleavage, rarely indistinct rhombohedral parting. fracture is conchoidal, transparent to subtranslucent. Crystals are hexagonal, usu. prismatic crystals striated crosswise and ended like hexagonal pyramids. q_milky.html  
Quartz [Rose] Gem and ornamental stones. Manufacture of glass, oscillators and filters in radio and telephone services. In watches(?) Tecto- silicate Is an important rock-forming mineral. Is a constituent of granite, sandstone, contact metamorphic rocks like gneiss, schist, etc. In hypothermal / mesothermal / epithermal veins. In most lode / disseminated hydrothermal replacement deposits. 2.65 7 Streak = white. Pink, rose-red. Vitreous, greasy. Pink, rose-red, or pale-rose quartz is called rose quartz (note to self: you have one). Generally no cleavage, rarely indistinct rhombohedral parting. fracture is conchoidal, transparent to subtranslucent. Crystals are hexagonal, usu. prismatic crystals striated crosswise and ended like hexagonal pyramids. q_rose.html  
Rhodonite Ornamental and gem stone Inosilicate Forms in metamorphic rocks and hydrothermal replacement deposits. 3.5 - 3.7 5.5 - 6 Streak = colorless. Brownish red, flesh-red, pink, rarely yellowish or greenish. may tarnish brown or black upon exposure. Vitreous Massive rhodonite is usually cut by narrow veins of dense black manganese oxide. Crystals are triclinic, rare, blocky, tabular, or square prismatic in form. Usually in fine-grained masses, granular, compact. Cleavage is good in two directions at nearly right angles. Fracture is conchoidal, uneven. Transparent to translucent. Can resemble rose quartz, but the cleavage is different. rhodonite.html  
Sodalite Gemstone Tecto- silicate Develops in nepheline syenite pegmatites. 2.2 - 2.3 5.5 - 6 Streak = white. Blue (usually dark to mottled blue) to bluish -gray, -white, -colorless, -green. Vitreous, greasy. Crystals are isometric, rare, usually dodecahedrons, compact, disseminated grains, nodular. Fracture is uneven to conchoidal. Transparent to translucent, fluorescent, brittle. Cleavage is poor, but in six directions. sodalite.html  
Sphalerite Principal zinc ore Sulfide Occurs with galena very often. In limestone deposits, hypothermal / mesothermal veins, and in massive / lode / disseminated hydrothermal replacement deposits. 3.9 - 4.1 3.5 - 4 Streak = light brown (always lighter than color). Yellow, brown, red, green, black; rarely white or pale gray. Resinous, adamantine, submetalic Cleavage is perfect in six directions (nice field mark). Crystals are isometric, tetrahedral, and dodecahedral. Faces often rounded. Fracture is conchoidal, brittle. Specimens w/ lots of iron are nearly opaque. Sometimes fluorescent. sphalerite.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Staurolite Right angled penetration twins are popular good-luck charms. Transparent single crystals are sometimes cut into gems. Neso- silicate Occurs in gneiss and schist of regional metamorphic rocks. 3.7 - 3.8 7 - 7.5 Streak = white. Yellowish brown, reddish to brownish black, weathering to gray. Vitreous, dull Very common twinned crystals, with two prisms often forming a right-angle cross. Cleavage is poor, one direction lengthwise. Fracture is uneven to subconchoidal. Translucent to opaque. Brittle. Single crystals are prismatic and show pseudohexagonal cross section. Twinned crystals show two individual crystals intergrown at nearly 60 or 90 degree angles. staurolite.html  
Sulfur/Sulphur Many uses, especially in manufacture of sulfuric acid. Tips of matches, batteries(?), etc. Native element. Generally deposited as a direct sublimation product from volcanic gases. Frequently occurs in basalt of volcanic rocks. 2.0 - 2.1 1.5 - 2.5 Streak = white. Always some shade of yellow. Resinous, adamantine Crystals are transparent and yellow. Orthorhombic, usually steep bipyramids, sometimes tabular, also granular, fibrous, compact, earthy. Fracture is conchoidal, very brittle. Cleavage is poor in two directions. Not easily confused w/ other minerals. sulfur.html  
Talc Many uses. It's talcum powder in cosmetics. Widely used as a lubricant and as insulation in electrical equipment. Phyllo-silicate Characteristic of metamorphic rocks derived from dolomite rock and peridotite. In regional and contact metamorphic rocks. 2.7 - 2.8 1 Streak = white. Apple-green, white. Pearly, greasy Greasy feel. Crystals are monoclinic, rare. Usually foliated, granular, fibrous. Massive talc is called soapstone. Fracture is uneven, sectile. Thin flakes are flexible, but not elastic. talc.html  
Topaz Gemstone. Orangish ones are called hyacinth. Neso- silicate High-temperature mineral and is generally found in igneous rocks and high-temperature veins. In granite pegmatites, rhyolite of volcanic rocks, and massive hydrothermal replacement deposits. 3.4 - 3.6 8 Streak = colorless. White, colorless, yellow, pink, bluish, greenish. Vitreous Cleavage is perfect in one basal direction. Fracture is subconchoidal and uneven. Transparent to translucent. Crystals are orthorhombic, usually in stubby to medium-long prismatic crystals striated lengthwise. topaz.html  
Tourmaline Widely used as semiprecious stone. Cyclo- silicate Forms in igneous and metamporphic rocks and veins. In granite pegmatites, regional metamorphic rocks, hypothermal veins, hydrothermal replacement deposits. 3.0 - 3.3 7 - 7.5 Streak = white. Black (schorl), blue (indicolite), pink and red (rubellite), brown(dravite), green, mulitcolored, rarely white. Vitreous Rounded triangular cross section of crystals. No cleavage. Fracture is uneven, conchoidal. Transparent to opaque. Brittle. Usually long, rod shaped, fibrous-looking (imo). Very watery looking. tourmaline.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid
                     
Tremolite Nephrite jade is used as gemstone, finely fibrous form is used as asbestos in many industrial applications. Ino- silicate Product of metamorphism. Found in hornfels of contact and serpentinites of hydrothermal metamorphic rocks. 2.9 - 3.1 5 - 6 Streak = colorless. White to dark gray, yellowish, pink to lilac, colorless. Vitreous, silky. Looks rather like non-translucent and bunched form of tourmaline. Cleavage is perfect in two directions, forming a diamond. Fracture is uneven. Small fibers are flexible. Crystals are monoclinic, usually in fibrous, radiating aggregates. Bladed, compact. tremolite.html  
Ulexite Source of boron and used in manufacturing of glass wool. Borate Develops in evaporite deposits of chemical sedimentary rocks. 1.9 2.5 Streak = white. White. Vitreous, satiny, silky. Crystals are triclinic, distinct crystals rare. usually in small, nodular, rounded or lenslike crystals, sometimes loose in texture. Fibrous. Can look like a koosh ball with thin needle-like spikes. Cleavage is perfect in one direction and good in second. Fracture is uneven and splintery. Transparent to translucent. ulexite.html  
Gold Gold ore. Jewelry, utensils, pins, etc. Native element Usually in clastic placer sedimentary deposits, veins, igneous rocks, and hydrothermal replacement deposits. 15.6 - 19.3 2.5 - 3 Streak = shiny golden yellow. Gold-yellow, brass-yellow, pale yellow. Does not tarnish. Metallic No cleavage. Crystals are isometric, commonly octahedral, dodecahedral, and cubit. Usually distorted. Malleable and ductile. Fracture is hackly. Specific gravity is a dead give-away. And everyone recognizes gold, right? gold.html  
Silver Silver ore. Jewelry, utensils, pins, etc. Native element Widely distributed in small amounts and occurs in volcanic rocks and hypothermal / mesothermal veins. 10.1 - 11.1 2.5 - 3 Streak = shiny silver-white to light lead-gray. Silver white, tarnish yellow, brown, black. Metallic No cleavage. Crystals are isometric, rare, cubic, octahedrons, and dodecahedrons or in groups of parallel cubs. Malleable and ductile. Fracture is hackly. Looks like platinum, but softer. Density is good field mark. Think silver spoons. silver.html  
Diamond Very valuable gemstone. Abrasive. Native element (C) Forms deep inside the earth with very high temperatures and pressures. Man-made diamonds are more likely to be fluorescent than natural ones. Found in sedimentary deposits and formed in periodite of plutonic rocks. 3.5 10 No streak. White, colorless, pale shades of yellow, red, orange, blue, green, brown, and black. Adamantine, greasy. Cleavage is perfect in four directions. Crystals are isometric, mostly octahedrons. Fracture is conchoidal, brittle. Some stones very fluorescent. Aggregates / abrasives have two varieties: Bort is roughly rounded globs w/ radial or confused structure and no cleavage (SG 3.5). Carbonado is opaque, and w/o cleavage. (SG 3.1 - 3.3). diamond.html  
                     
Rock Name Eco. Imp. Class. Formation S.G. Hardn. Colors Luster Characteristics Image URL H. Acid



<< home || definitions || email || scioly >>