Minerals

MineralsWhat are they? Why are they important?How are they identified?

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What are minerals?A naturally forming inorganic (non-living) solidCrystal structure due to internal arrangement of atoms.Specific chemical composition

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Minerals are inorganicNever been aliveExample: copper, quartz, calcite.Fossils are NOT minerals- they were once livingNatural gas and oil are NOT minerals- they came from once-living organisms

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Why are minerals important?Essential natural resourcesIf it cant be grown it must be minedMining is taking valuable minerals out of the Earth.

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What do we mine for?Metals- buildings, homes, plumbing, electrical, manufacturing, transportationRocks- buildings, roads, manufacturingJewelry, currency, artHealth, medicine

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Mineral Identification Properties1. Hardness2. Luster3. Streak4. Color5. Cleavage6. Fracture

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Mohs Hardness ScaleHardness is the ability to scratch another mineralMohs uses 10 relatively common minerals to compare their relative hardnessUses common items of known hardness to compare with ten minerals (fingernail, steel nail, glass plate, copper penny)Very important in mineral identification

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Mohs Hardness Scale1. Talc Softest mineral2. GypsumGypsum can scratch talc.

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Mohs Hardness testA fingernail can scratch both talc(1) and gypsum(2)A fingernail is assigned the hardness number of 2.5

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3. CalciteCalcite can scratch gypsum4. Fluoritefluorite can scratch calcite and softer minerals

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Mohs Hardness TestA copper penny has a hardness of 3A copper penny can scratch minerals softer than a 3

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5. ApatiteCan scratch Fluorite6. Potassium FeldsparK-sparK spar can scratch all softer minerals. None of the softer minerals can scratch it.

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7. Quartzso hard it can scratch glass8. TopazTopaz is harder than quartz

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9. CorundumCan scratch Topaz10. Diamondis the hardest natural substance knownIt is harder than all other minerals

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LusterQuality and intensity of light reflecting off the faces of the crystalNon-metallicMetallic

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Non-metallic lusterShiny like a metalMetallic lusterDull/ EarthyWaxy, greasy or soapyGlassyPearlySilky

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Vitreous lusterGlasslikeMost commonEx. Quartz

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Waxy LusterHas the look of waxExamples: chert,smithsonite

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Earthy/Dull LusterNon-reflective surfaceDirt-like appearanceExamples: barite roses; bauxite, limonite

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Pearly LusterHas the shine of a pearlEx. Mica

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Silky LusterLooks like silkUsed to describe fibrous minerals, such as asbestos

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Metallic LusterLooks likeshiny metalCopper, silver, gold, platinum,

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Mineral StreakThe color of the powder left when a mineral is rubbed on a streak plateThe ability/inability of a mineral to create a streak helps ID it

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Mineral StreakWhen rubbed on a ceramic tile, some minerals leave certain color streaks.(EX) Grey hematite leaves a red streak

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ColorColor is based on what wavelength of light is absorbed and reflected.Color is the LEAST reliable mineral ID testMany different minerals have the same color.The same mineral can often have different colors

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ID by colorSulfur

copper

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Same mineral-Different colorsquartz

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Same Color- Different MineralsGypsumCalciteAlbiteHalite

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CleavageHow a mineral breaks or splits along planes of their crystal structure Cleaves along the same parallel plane over and over againOccurs in minerals with specific planes of weaknessSeveral different types of cleaving

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Octahedral cleavageMultiple cleavage planes-Fluorite

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Cubic Cleavage90 degree anglesSix-sided cubeGalenaHalite

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Rhombohedra CleavageCalcite

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FractureMineral breaks along uneven lines and results in rough and curved surfaces.Conchoidal Fracture- looks like a clam shell.Due to atomic configuration.

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Other Properties used to ID minerals

MagnetismAcid test calcium bubbles when touched with an acid: calciteFluorescence glow under UV lightSalty- contain naturally occurring salt: (halite)

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