Minerals

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Minerals

  1. 1. Minerals • Natural • Solid • Inorganic • Definite chemical composition • Crystal structure due to internal arrangement of atomshttp://www.minerals.net/gemstone/index.htm
  2. 2. General Facts about Minerals• Between 2 - 3,000 have been identified• A few are “native elements” -- made of only one element, such as sulfur, gold. copper, and graphite (carbon)• Most are compounds, especially the silicate group (Si, O).• Other important groups are oxides, carbonates, and sulfides.
  3. 3. Silica Tetrahedron• Made up of one silicon atom (Si) and four oxygen atoms (O).• Basis for most rocks on Earth.
  4. 4. Less than a dozen are common in most rocks• Quartz • Olivine• Feldspar (group) • Amphibole (group)• Muscovite (white • Magnetite, limonite, mica) and other iron• Biotite (black mica) oxides• Calcite • Pyrite• Pyroxene
  5. 5. Common uses include:• Aluminum--packaging, transport, building• Beryllium--gemstones, fluorescent lights• Copper--electric cables, wires, switches• Feldspar--glass and ceramics• Iron--buildings, automobiles, magnets• Calcite--toothpaste, construction• http://www.mii.org/commonminerals.php
  6. 6. Minerals are identified by their key characteristics • Crystal Structure (form) • Cleavage vs fracture • Color – Least reliable • Streak – true color • Hardness
  7. 7. Moh’s Scale of Hardness Finegernail – 2.5 Penny – 3.0 Glass – 5.0 Scratch Plate Diamond scratches everything!!
  8. 8. Mineral Identification (cont’d) • luster • density (specific gravity) • special properties --reaction to acid --fluorescence --salty taste --magnetism
  9. 9. Crystal Structure (Form)• External structure due to internal arrangement of the atoms• Six basic groups of shapes, with about three dozen variations http://www.minerals.net/mineral/carbonat/aragonit/aragoni1.htm
  10. 10. Mineral cleavage/fracture• Some minerals split along flat surfaces when struck hard--this is called mineral cleavage• Other minerals break unevenly along rough or curved surfaces--this is called fracture• A few minerals have both cleavage and fracture
  11. 11. Color • results from ability to absorb some wavelengths and reflect others • some minerals have characteristics colors • others vary due to chemical differences or impurities (atoms mixed inside the main elements)http://www.minerals.net/mineral/carbonat/calcite/images/4assortd.htm
  12. 12. Streak• Color of the powder when rubbed on a “streak plate” (unglazed porcelain)• May be same as hand- specimen or different• Some paint is based on powdered minerals (streaks).http://www.minerals.net/mineral/oxides/hematite/hematit6.htm
  13. 13. Mineral Hardness • Ability to scratch another mineral • Mohs scale from 1 (talc) to 10 (diamond) • Quartz (most common mineral and most dust particles) is 7http://mineral.galleries.com/minerals/elements/diamond/diamond.htm
  14. 14. • Describes how lightLuster reflects off the surface • Main categories are “metallic” and “non- metallic” • Non-metallic includes “dull,” glassy,” waxy,” “pearly,” and othershttp://www.min erals.net/mineral/sulfi des/pyrite/pyrite2.htmhttp://www.minerals.net/mineral/sulfides/pyrite/pyrite2.htm
  15. 15. Density (Specific Gravity)• All minerals have density (mass / volume), but some are very dense• Examples include galena, magnetite, and gold• Specific Gravity is the density of the mineral compared with density of water http://www.minerals.net/mineral/elements/gold/gold1.htm
  16. 16. Special Characteristics-- the “Acid Test” Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)
  17. 17. Special Characteristics-- Fluorescence • Some minerals will glow when placed under short-wave or long-wave ultraviolet rays • Franklin and Ogdensburg NJ are famous for their fluorescent mineralshttp://www.sterlinghill.org/Tour%20information.htm
  18. 18. Special Characteristics-- Salty Taste • DO NOT TASTE MOST MINERALS! • Halite is the exception--it will taste saltyhttp://mineral.galleries.com/scripts/item.exe?LIST+Minerals+Halides+Halite
  19. 19. Special Characteristics-- Magnetism • Many iron minerals will produce an invisible magnetic force field • “Lodestone” was used by Vikings more than 1,000 years ago as compasseshttp://www.minerals.net/mineral/oxides/magnetit/magneti4.htm
  20. 20. Useful Web Sites• www.mii.org• www.mineral.galleries.com/minerals• www.mineral.net• www.usgs.gov

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