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Mineral Identification

Mineral Identification. Objective. 3 Define chemical and physical properties of minerals to include luster, hardness, cleavage, fracture, streak , color, specific gravity, and special traits. Enduring Understanding. Minerals are the building blocks of rocks. Mineral Identification.

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Mineral Identification

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  1. Mineral Identification

  2. Objective 3 Define chemical and physical properties of minerals to include luster, hardness, cleavage, fracture, streak, color, specific gravity, and special traits.

  3. Enduring Understanding • Minerals are the building blocks of rocks.

  4. Mineral Identification • With more than 3,000 minerals in Earth’s crust how does one go about identifying an unknown mineral?

  5. Mineral Identification • Geologists rely on several simple tests that are based on a mineral’s physical and chemical properties. It is usually best to use a combination of tests rather than just one to identify minerals

  6. Mineral Properties • Color is one of the most noticeable but least reliable characteristics

  7. Mineral Properties • Sometimes caused by the presence of trace elements or compounds Quartz

  8. Mineral Properties • Streak is the color of the mineral when it is broken up into a powder and is a much more reliable identification method because it rarely changes Both of these samples are hematite; both have a reddish-brown streak

  9. Mineral Properties • Streak is easily determined by rubbing the mineral across an unglazed porcelain plate

  10. Mineral Properties • Streak is used to distinguish pyrite from gold

  11. Mineral Properties • Streak is used to distinguish pyrite from gold Pyrite Gold

  12. Mineral Properties • Luster is the way a mineral reflects light from its surface and is caused by differences in mineral chemical compositions

  13. Mineral Properties • Either metallic or nonmetallic (dull, pearly, waxy, silky)

  14. Mineral Properties • Texture describes how a mineral feels to the touch • Rough, smooth, ragged, greasy, soapy, glassy

  15. Mineral Properties • Hardness is a measure of how easily a mineral can be scratched and is determined by the arrangement of it’s atoms.

  16. Mineral Properties • The Mohs hardness scale is used to compare a sample to the hardness of ten known minerals

  17. Mineral Properties • Cleavage determines whether a mineral will split easily and evenly along one or more flat planes

  18. Mineral Properties • Mica has perfect cleavage in one direction • Halite has cubic cleavage (3 planes)

  19. Mineral Properties • Fracture means the mineral is tightly bonded and breaks with rough or jagged edges • Quartz has fracture

  20. Mineral Properties • Specific Gravity compares the weight of the mineral to an equal volume of water at 4 degrees C

  21. Mineral Properties • Special Properties such as light reflection and reactions to acids are also useful tools

  22. Mineral Properties • Calcite fizzles when in contact with HCl

  23. Mineral Properties • Calcite also can cause double images

  24. Mineral Properties • Magnetite will attract iron

  25. Mineral Properties • Sulfur produces a rotten egg odor

  26. Minerals General Notes

  27. Minerals

  28. Minerals • have four characteristics 4

  29. Naturally occurring— • formed by processes on or inside • Earth with no input from humans

  30. Inorganic— • not made by life processes Living

  31. Element or compound with a definite chemical composition

  32. Orderly arrangement of atoms; all minerals are crystalline solids

  33. Crystal—solid with atoms arranged in orderly, repeating patterns

  34. Some crystals form from magma, hot melted rock below the Earth’s surface.

  35. When magma cools slowly, crystals are large. When magma cools quickly, crystals are small.

  36. Crystals can form from solutions as water evaporates or if too much of a substance is dissolved in water.

  37. Mineral groups are defined by their composition. • Silicates contain silicon, oxygen, and one or more other elements; they include most common rock-forming minerals. • Silicon and oxygen are the two most abundant elements in Earth’s crust; they form the building blocks of many minerals.

  38. DISCUSSION QUESTION: • What processes can cause crystals to form?

  39. DISCUSSION QUESTION: • What processes can cause crystals to form? Crystals form from cooling magma, from evaporating solutions, and from solutions in which too much of a substance is dissolved.

  40. Mineral Identification • Color and appearance are not enough to distinguish most minerals.

  41. Hardness is a measure of how easily a mineral can be scratched; the Moh’s scale compares mineral hardness.

  42. Talc - easily scratched by the fingernail • Gypsum - just scratched by the fingernail • Calcite - scratches and is scratched by a copper coin • Fluorite - not scratched by a copper coin and does not scratch glass • Apatite - just scratches glass and is easily scratched by a knife • Orthoclase - easily scratches glass and is just scratched by a file • Quartz - (amethyst, citrine, tiger's-eye, aventurine) not scratched by a file • Topaz - scratched only by corundum and diamond • Corundum - (sapphires and rubies) scratched only by a diamond • Diamond - scratched only by another diamond

  43. 1 - Talc

  44. 2 - Gypsum

  45. 3 - Calcite

  46. 4 - Flourite

  47. 5 - Apatite

  48. 6 - Orthoclase

  49. 7 - Quartz

  50. 8 - Topaz

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