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Minerals and Resources

Minerals and Resources. Minerals Versus Rocks. Mineral - any naturally formed, solid chemical element or compound that has a definite composition and crystalline structure. Rock - any natural, solid aggregate material, usually made of minerals.

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Minerals and Resources

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  1. Minerals and Resources

  2. Minerals Versus Rocks Mineral - any naturally formed, solid chemical element or compoundthat has a definite composition and crystalline structure Rock - any natural, solid aggregate material, usually made of minerals All minerals are rocks, but not all rocks are made of minerals Quartz Granite

  3. Mineral Properties • Chemical composition • Crystalline shape • Hardness • Color • Streak • Luster • Cleavage • Fracture • Specific Gravity • Magnetism These properties are used toidentify different minerals

  4. Chemical Composition Extremely important for the minerals industry. Often want an element or compound in mineral, and not necessarily the mineral itself Ex.: iron and sulfur from iron pyrite (FeS2) Identifying a mineral by chemical composition requires submitting a sample for chemical analysis; can be time consumingand expensive

  5. Crystalline Shape Useful for identification; of little use for industry, as crystallineshape can be replicated in lab Shape normally determined by chemical formula Jewelry about the only use for this property; even then, the fact that crystals can be artificially created means that their value isartificial, as well Hope Diamond

  6. Hardness Mho’s Scale Relative scale based upon what mineral will scratch what mineral Ex. Orthoclase will scratch apatite, but quartz will scratch orthoclase 1 = Talc 2 = Gypsum 3 = Calcite 4 = Fluorite 5 = Apatite 6 = Orthoclase 7 = Quartz 8 = Topaz 9 = Corundum 10 = Diamond Fingernail is about a 2.5; steel nail = 5.5 Diamond is hardest, which means that itdoes have some industrial application Hardness does not relate to elemental scarcity or value

  7. Color and Streak Color - what color unmolested mineral appears to beStreak - color of ground mineral These two can be radically different. Ex.: Iron pyrite color is gold (fool’s gold); streak is blackHematite is black/gray; streak is red-brown Color is unreliable as identifier since impurities can change it;streak is more reliable

  8. Other Properties Depending upon mineral, will use a variety of other identifiersMagnetism - used to identify iron oresCleavage - used to identify minerals like mica and gypsum thatform crystals that loosely bond together Fracture - helps to identify minerals with crystalline shapes thatdo not cleave

  9. Mineral Types Based upon the key elements in the chemical composition,minerals are grouped into subcategories • Silicates (feldspars, garnets, micas, olivine, quartz, clay minerals) • Native Elements (diamond, sulfur, gold) • Sulfides (galena, pyrite, millerite, sphalerite) • Sulfates (barite, celestite, gypsum, secondary sulfates) • Oxides (goethite, hematite, ilmenite, limonite, uranium minerals) • Carbonates (calcite, dolomite, other iron-carbonate and others) • Phosphates (apatite, vivianite, pyromorphite) • Halides (fluorite, halite)

  10. Silicates The largest group of minerals (30% of all minerals; 90% of wholecrust); defined by having SiO4 tetrahedraIncludes some gemstones such as tourmaline and topazAlso has useful minerals such as talc, kaolin, and micaRocks made from silicates very useful for road and building materials

  11. Native Elements Contains all of the metals (gold, silver, copper, etc.) and metal alloysAlso includes diamonds and graphite (carbon) Rare to find elements in their natural state; oftentimes, a primary method of metal extractions is from some other class Ex. Copper and lead from sulfide minerals

  12. Strategic Resources Defn. - resources that a country uses, but cannot produce enoughto meet demand If cannot guarantee supply, economy could be hurt if suppliescut; Ex. OPEC oil embargo of 1973 Wealthy nations try to stockpile surplus to act as buffer againstoutside forces affecting economy

  13. Mining Hollywood image of old manwith mule, pick axe, anddynamite all but disappeared Most economic mining done on huge scale with big equipment Vulcan Materials pit mine, Kennesaw, GA, 1993 • Open pit - dig deep into the ground, exposing new rock to surface • Stripmining - shallow mine over large area • Underground mining - tunnels

  14. Open Pit Mineral ore dug from deep holecreated in the surface. Walls of pit have roads built into them for cranes, trucks, etc. to be able to get to bottomEconomics of recovery have to constantly be re-evaluated, as holemust get wider as go deeper (walls are the road system)

  15. Stripmine Differs from open pit in horizontal extantStripmines are going after near horizontalseam of materials that are near the surfaceOverburden is stripped from seam, and then mineral is extractedOnce mineral removed, overburden putback on topFederal law now requires remediation

  16. Underground Mining Pickaxe and dynamite have been replaced by large tunneling equipment that doesthe job safer and fasterMust leave some pillars of material behind, lest a cave-inensueMost dangerous form of mining Miner safety in jeopardy from cave-ins and dust (black lungdisease)

  17. Other Techniques Hydraulic mining - sediments are blasted from hillside with waterjets; sediment is sent through sluice boxes; not done much in U.S., but is done many other places (South America) Dredging - similar to hydraulic mining, with the exception being thatthe sediment is scooped out of the ground instead of being blastedout with water

  18. Mining Pollution • Water passing through mine leaches toxic chemicals • Tailings piles and ponds erode and contain toxics • Processing chemicals are toxic and sometimes released • Land slumpage when cave-ins occur • Underground fires can burn for decades • Many mines are abandoned when economics fail • Energy used for entire process is large Pictures from Berkeley Pit in Butte Montana Superfund Sites

  19. Processing Some rocks and minerals take very little processingEx: crushed rock for roads and construction material Others take an incredible amount of energy and produce greatquantities of wasteSmelting - heating metal ores to extreme temperature to releasemetal; gaseous vapors are toxic and often acidicLeach extraction - pour acid or base on crushed piles of ore, extract metal from leachate by electrolysis; crushed ore is leftto contaminate water supply when finished, with acid or basestill present

  20. Recycling • Besides saving environmental damage for extraction and processing, can save huge quantities of energy • Recycling aluminum saves 95% • Recycling glass saves 25% • Recycling steel saves between 60-75% • Recycling plastic saves 33% • of the energy needed to make them from virgin materialsRecycling just one aluminum can will save enough energy torun a 100W lightbulb for 20 hours

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