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Minerals

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Minerals

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  1. Minerals

  2. What is a mineral? • Naturally occurring • inorganic (no living thing or remains) • Solid • Definite shape ( arranged in an orderly pattern) • definite chemical composition

  3. Is it inorganic? • Coal? • No, it is not a mineral- How is it made? • magnetite • Yes, a mineral • pearl • No, not a mineral- How is it made?

  4. Does it occur naturally? • Quartz • yes, a mineral- one of the last minerals to form from a magma chamber. • Silver • yes, a mineral • steel • no, not a mineral- How is it made?

  5. Solid in crystalline form? • Petroleum • no, not a mineral- What is its natural form? • mercury • no, not a mineral- What is its natural form? • glass • not a mineral- What is its form? • amorphous

  6. Definite chemical composition? • Calcium • yes, Ca a mineral • Graphite • yes, C • Concrete • no, not a mineral- Why?

  7. Rock forming minerals • Over 3000 minerals • only 20 are common, these are rock forming minerals • two main groups- silicates and nonsilicates

  8. Silicates • 96% of the crust • contain silicon (Si) and Oxygen (O) • Feldspars are the most common silicate minerals, contain Ca, K, and Na • Examples- Orthoclase and plagioclase • Ferromagnesium- contain Fe and Mg

  9. Nonsilicates • 4% of the crust • No silica • Six major groups • carbonates-ex. Calcite • halides- ex halite • native elements- Made of one element ex. copper and silver • oxides- hematite and corundum • sulfates- gypsum • sulfides- galena, pyrite

  10. Crystal Structure • Specific geometric arrangement of atoms or ions • Crystal = natural solid with a definite shape • Can be seen under microscope or with the aid of x rays

  11. Identifying Minerals • Characteristics of Minerals • Each mineral has specific properties that provide useful clues for identifying minerals. • Optical properties- properties will be identified by looking at the mineral. • Tests- tools are used to run tests on the mineral.

  12. Optical PropertiesColor • Most easily observed • ex. Sulfur is bright yellow, azurite is deep blue • least reliable characteristic • quartz consists of many colors • weathering may hide true color

  13. Luster • Light reflected from the surface of a mineral • metallic luster- like polished metal like silver • All others are non metallic • vitreous luster- reflects like glass • pearly luster • adamantine- brilliant luster ex. Diamond or gems • other lusters include: waxy, greasy, dull, earthy

  14. Crystal Shape • Regularly shaped particles, or pattern. • Most crystal shapes are hard to identify. • six crystal systems • cubic ex. Halite, Pyrite • orthorhombic ex. Sulfur • tetragonal ex. Chalcopyrite • hexagonal ex. Plagioclase, Orthoclase • monoclinic ex. Micas • triclinic ex. Kyanite

  15. Cleavage • The tendency to split along certain flat surfaces and is related to types of bonds • ex. Mica (general name) splits easily in one direction, it has one perfect cleavage ( splits in parallel sheets) • Example- biotite and muscovite

  16. Fracture • Some minerals do not break along cleavage planes • instead they fracture or break unevenly into curved or irregular pieces • splintery or fibrous fracture- looks like pieces of broken wood • conchoidal- curved surfaces like the inside of a shell

  17. Simple TestsStreak Test • The color of a mineral in powdered form • observed by rubbing the mineral against a piece of unglazed ceramic tile called a streak plate • the streak is not always the same color as the mineral • mineral that have a hardness higher than the streak plate can not be tested

  18. Hardness Test • The ability to resist scratching • hardness does not mean resistance to cleavage or fracture • the hardness of an unknown mineral may be determined by using Moh’s Hardness Scale • -this scale lists 10 minerals in order of increasing hardness • -Softest is talc with a hardness of 1 • The hardest is diamond with a hardness of 10

  19. Moh’s Hardness Scale • Mineral hardness common test • talc 1easily scratchedby fingernail • gypsum 2 can be scratched by fingernail • calcite 3 can not scratch a copper penny • fluorite 4 can easily scratch a penny • Apatite 5 can barely scratch glass • Feldspar 6 can scratch glass • quartz 7 very easily/deeply scratches steel and glass • topaz 8 scratches quartz • corundum 9 no simple tests • diamond 10 scratches everything

  20. Specific Gravity • The ratio of the weight of the mineral to the weight of an equal volume of water. • Each mineral has its own specific gravity • Can be used to identify a mineral

  21. Acid Test • Used to easily identify calcite A drop of HCl dropped onto Calcite will cause it to effervesces. The bubbles are CO2 gas. • Dolomite also responds to the acid test but not as violently and only in powdered form.

  22. Special Properties • Magnetism- Can attach a magnet • Fluorescence- the ability to glow under UV light ex. Calcite appears red under UV • Phosphorescence- minerals that continue to glow after a UV light is removed.ex sphalerite

  23. Special Properties con’t • Double refraction- crystals that bend light in such a way that they produce a double image of any object viewed. • Radioactivity- certain atoms have unstable electron or neutron arrangements. These minerals activate a Geiger counter.

  24. End of Minerals