what are they? why are they important? how are they identified?

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  • What are they? Why are they important? How are they identified?
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  • What are minerals? A naturally forming inorganic (non-living) solid Crystal structure due to internal arrangement of atoms. Specific chemical composition
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  • Minerals are inorganic Never been alive Example: copper, quartz, calcite. Fossils are NOT minerals- they were once living Natural gas and oil are NOT minerals- they came from once- living organisms
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  • Why are minerals important? Essential natural resources If it cant be grown it must be mined Mining is taking valuable minerals out of the Earth.
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  • What do we mine for? Metals- buildings, homes, plumbing, electrical, manufacturing, transportation Rocks- buildings, roads, manufacturing Jewelry, currency, art Health, medicine
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  • Mineral Identification Properties 1. Hardness 2. Luster 3. Streak 4. Color 5. Cleavage 6. Fracture
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  • Mohs Hardness Scale Hardness is the ability to scratch another mineral Mohs uses 10 relatively common minerals to compare their relative hardness Uses 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 Scale 1. Talc Softest mineral 2. Gypsum Gypsum can scratch talc.
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  • Mohs Hardness test A fingernail can scratch both talc(1) and gypsum(2) A fingernail is assigned the hardness number of 2.5
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  • 3. Calcite Calcite can scratch gypsum 4. Fluorite fluorite can scratch calcite and softer minerals
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  • Mohs Hardness Test A copper penny has a hardness of 3 A copper penny can scratch minerals softer than a 3
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  • 5. Apatite Can scratch Fluorite 6. Potassium Feldspar K-spar K spar can scratch all softer minerals. None of the softer minerals can scratch it.
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  • 7. Quartz so hard it can scratch glass 8. Topaz Topaz is harder than quartz
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  • 9. Corundum Can scratch Topaz 10. Diamond is the hardest natural substance known It is harder than all other minerals
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  • Luster Quality and intensity of light reflecting off the faces of the crystal Non-metallic Metallic
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  • Non-metallic luster Shiny like a metal Metallic luster Dull/ Earthy Waxy, greasy or soapy Glassy Pearly Silky
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  • Vitreous luster Glasslike Most common Ex. Quartz
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  • Waxy Luster Has the look of wax Examples: chert, smithsonite
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  • Earthy/Dull Luster Non-reflective surface Dirt-like appearance Examples: barite roses; bauxite, limonite
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  • Pearly Luster Has the shine of a pearl Ex. Mica
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  • Silky Luster Looks like silk Used to describe fibrous minerals, such as asbestos
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  • Metallic Luster Looks like shiny metal Copper, silver, gold, platinum,
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  • Mineral Streak The color of the powder left when a mineral is rubbed on a streak plate The ability/inability of a mineral to create a streak helps ID it
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  • Mineral Streak When rubbed on a ceramic tile, some minerals leave certain color streaks. (EX) Grey hematite leaves a red streak
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  • Color Color is based on what wavelength of light is absorbed and reflected. Color is the LEAST reliable mineral ID test Many different minerals have the same color. The same mineral can often have different colors
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  • ID by color Sulfur copper
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  • Same mineral- Different colors quartz
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  • Same Color- Different Minerals Gypsum Calcite Albite Halite
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  • Cleavage How a mineral breaks or splits along planes of their crystal structure Cleaves along the same parallel plane over and over again Occurs in minerals with specific planes of weakness Several different types of cleaving
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  • Octahedral cleavage Multiple cleavage planes- Fluorite
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  • Cubic Cleavage 90 degree angles Six-sided cube Galena Halite
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  • Rhombohedra Cleavage Calcite
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  • Fracture Mineral 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 Magnetism Acid test calcium bubbles when touched with an acid: calcite Fluorescence glow under UV light Salty- contain naturally occurring salt: (halite)


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