Identifying Minerals


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Identifying Minerals

  1. 1. What is a mineral? <ul><li>Found in nature </li></ul><ul><li>Inorganic: not made from living things </li></ul><ul><li>Always in a solid form </li></ul><ul><li>Has a crystal structure </li></ul><ul><li>Definite Chemical composition: always has the same elements is the same amount </li></ul>
  2. 2. Identifying Minerals Chapter 2 Section 1 p. 49-54
  3. 3. Minerals <ul><li>Each mineral has its own specific properties that can be used to identify it. </li></ul><ul><li>Learning these properties will make it easy to identify minerals. </li></ul>
  4. 4. Hardness <ul><li>One of the best clues to use is hardness. </li></ul><ul><li>Mohs hardness scale – invented by Friedrich Mohs in 1812 </li></ul><ul><li>Ranks 10 minerals from softest to hardest </li></ul>
  5. 5. Mohs hardness scale <ul><li>1 - Talc – softest known mineral. It flakes easily when scratched by fingernail. </li></ul><ul><li>2 – Gypsum – a fingernail can easily scratch it. </li></ul><ul><li>3 – Calcite – A fingernail cannot scratch it, but a copper penny can. </li></ul>
  6. 6. Mohs continued <ul><li>4 – Fluorite – A steel knife can easily scratch it. </li></ul><ul><li>5 – Apatite – A steel knife can scratch it. </li></ul><ul><li>6 – Feldspar – Cannot be scratched by a steel knife, but it can scratch window glass. </li></ul><ul><li>7 – Quartz – Can scratch steel and hard glass easily. </li></ul>
  7. 7. Mohs continued <ul><li>8 – Topaz – Can scratch quartz. </li></ul><ul><li>9 – Corundum – Can scratch topaz. </li></ul><ul><li>10 – Diamond – Hardest known mineral. Diamond can scratch all other substances. </li></ul>
  8. 8. Color <ul><li>Color is easy to identify </li></ul><ul><li>Color can be used only to identify a few minerals that always have their own characteristic color. </li></ul><ul><li>Azurite – always blue </li></ul><ul><li>Malachite – always green </li></ul>
  9. 9. Streak <ul><li>The streak of a mineral is the color of its powder. </li></ul><ul><li>You rub the mineral against a streak plate to see the powder. </li></ul><ul><li>Pyrite – gold in color – black streak </li></ul><ul><li>Gold – gold in color – golden yellow streak </li></ul>
  10. 10. Luster <ul><li>Luster is how the mineral reflects light </li></ul><ul><li>Minerals with metals in them are often shiny. </li></ul><ul><li>Quartz is glassy. </li></ul><ul><li>Other terms to describe Luster are earthy, waxy, and pearly. </li></ul>
  11. 11. Density <ul><li>Each mineral has a characteristic density </li></ul><ul><li>Density = Mass per unit volume </li></ul><ul><li>No matter what size of the sample, the density will always be the same. </li></ul><ul><li>To find the density, measure the mass with a balance and then put the sample in water to find the volume. Use the formula to calculate. </li></ul>
  12. 12. Cleavage <ul><li>A mineral that splits apart easily along flat surfaces has the property of cleavage . </li></ul><ul><li>How the atoms in the crystal are arranged will determine if the mineral has cleavage. </li></ul>
  13. 13. Fracture <ul><li>Most minerals do not split apart evenly. </li></ul><ul><li>Fracture describes how a mineral will look when it breaks apart in an irregular way. </li></ul><ul><li>Quartz – shell-like shaped fracture, looks like chipped glass </li></ul><ul><li>Pure metals – have hackly fracture – form jagged points </li></ul><ul><li>Some soft minerals that crumble easily have a earthy fracture. </li></ul><ul><li>Minerals that form rough, irregular surfaces when they are broken have an uneven fracture. </li></ul>
  14. 14. Special properties <ul><li>Fluorescence – minerals that glow under ultraviolet light </li></ul><ul><li>Magnetism occurs in a few minerals. </li></ul><ul><li>A Few minerals are radioactive. </li></ul><ul><li>Some minerals will react chemically with acid. </li></ul><ul><li>Some with conduct a small electric current. </li></ul>
  15. 15. Essential Questions Please answer in complete sentences <ul><li>What properties can you use to determine the type of mineral? </li></ul><ul><li>Describe how you can test a mineral to determine its hardness, density, and streak. </li></ul><ul><li>How are cleavage and fracture similar? How are they different? </li></ul><ul><li>Explain why you can’t rely on any single test or property when you are trying to identify a mineral. </li></ul>