6th Grade Chapter 15


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6th Grade Chapter 15

  1. 1. Earths Rocks & Minerals Chapter 15
  2. 2. Minerals <ul><li>Minerals are very important in everyday life. Minerals, bricks, and glass are some examples of how we use minerals. </li></ul><ul><li>Mineral - is a naturally occurring, inorganic solid with a definite chemical composition and an orderly arrangement of atoms. </li></ul><ul><li>There are about 4,000 minerals on Earth. </li></ul>
  3. 3. Mineral Characteristics <ul><li>All minerals are formed by natural processes. These processes occur on or inside the Earth with no human interaction. </li></ul><ul><li>Ex: Salt forms by the natural evaporation of salt water. This type of salt comes from a mineral called Halite. </li></ul><ul><li>Salt water solution made in a lab is not a mineral. </li></ul>
  4. 4. Mineral Characteristics <ul><li>2) Minerals are inorganic- this means that there is no Carbon is present in minerals. </li></ul><ul><li>3) Every mineral is an element or compound with a definite chemical composition. </li></ul><ul><li>4) All minerals are crystalline solids . And all crystals have a definite volume and shape. </li></ul>
  5. 5. Crystals <ul><li>Crystal atoms are arranged in a pattern that is repeated over and over again. </li></ul><ul><li>Ex: Graphite atoms are arranged in layers. </li></ul><ul><li>Opal- is not a mineral because it has no repeated atom patterns. </li></ul>
  6. 6. Structure of Minerals <ul><li>All minerals are crystalline solids. </li></ul><ul><li>Crystalline solids - are solids in which the atoms are arranged in an orderly repeated fashion. </li></ul><ul><li>This does not mean that all minerals look like crystals. </li></ul><ul><li>Ex: Rose quartz doesn’t look like a crystal because it develops in tight spaces. </li></ul><ul><li>Clear quartz forms in open spaces and its appearance is clearly crystal shaped. </li></ul>
  7. 7. Crystal vs. Non-Crystal
  8. 8. Crystal Formation <ul><li>Crystals form in two ways: </li></ul><ul><li>From cooling Magma </li></ul><ul><li>Could form in solution </li></ul>
  9. 9. Crystal Formation from Magma <ul><li>The type of atoms present and the amount will determine what mineral is produced. </li></ul><ul><li>When magma cools slowly large crystals form. </li></ul><ul><li>When magma cools quickly then small crystals form. </li></ul>
  10. 10. Crystal Formation from Solution <ul><li>Crystals form minerals dissolved in water. </li></ul><ul><li>When water evaporates, ions are left behind that can combine to form crystals like halite. (salt) </li></ul><ul><li>Or </li></ul><ul><li>If there is too much substance in solution the crystals could form in the solution </li></ul>
  11. 11. Quartz and Feldspar Pics
  12. 12. How to Identify Minerals <ul><li>We identify minerals by some very specific physical features and properties. </li></ul><ul><li>Color is one way to tell the difference between two minerals but color alone is not enough. </li></ul><ul><li>Ex: Gold and pyrite both have the same color, but they are two very different minerals. Pyrite has very little value compared to gold. </li></ul><ul><li>So to tell these two apart you have to look at other properties. </li></ul>
  13. 13. Gold and Pyrite
  14. 14. 5 Major properties used to distinguish between minerals <ul><li>Hardness </li></ul><ul><li>Luster </li></ul><ul><li>Specific gravity </li></ul><ul><li>Streak </li></ul><ul><li>Cleavage/ fracture </li></ul>
  15. 15. 5 major properties <ul><li>Hardness- This is the measure of how easily a mineral can be scratched. </li></ul><ul><li>Ex: Talc, a very soft mineral can be scratched with just your finger nail. </li></ul>
  16. 16. Hardness of Minerals <ul><li>Diamonds, on the other hand are the hardest mineral. </li></ul><ul><li>The only this that can scratch a diamond is another diamond. </li></ul><ul><li>Remember scratch and break are not the same. If hit hard enough a diamond will shatter. </li></ul>
  17. 17. Mohs Scale <ul><li>In 1812 the Mohs scale of mineral hardness was devised by the German mineralogist Frederich Mohs (1773-1839), who selected the ten minerals because they were common or readily available. The scale is not a linear scale, but somewhat arbitrary. </li></ul><ul><li>Hardness of some other items: </li></ul><ul><li>2.5 Fingernail </li></ul><ul><li>2.5–3 Gold, Silver </li></ul><ul><li>3 Copper penny </li></ul><ul><li>4-4.5 Platinum </li></ul><ul><li>4-5 Iron </li></ul><ul><li>5.5 Knife blade </li></ul><ul><li>6-7 Glass </li></ul><ul><li>6.5 Iron pyrite </li></ul><ul><li>7+ Hardened steel file </li></ul>
  18. 18. 5 major properties <ul><li>2) Luster - This is the way a mineral reflects light. </li></ul><ul><li>This reflection could be metallic, meaning it shines like a metal, or non-metallic or dull or glassy looking. </li></ul>
  19. 19. Luster
  20. 20. 5 major properties <ul><li>3) Specific Gravity- This is the ratio of the minerals weight compared to the weight of an equal volume of water. </li></ul><ul><li>Ex: Specific Gravity of Gold is 19:1 or 19. </li></ul><ul><li>This means that gold is 19x heavier that water. </li></ul><ul><li>How could you find out the volume of a solid? </li></ul>
  21. 21. 5 major properties <ul><li>4) Streak - Is the color of a mineral when it is in powder form. </li></ul><ul><li>So if we have a solid mineral we would streak it across a piece of porcelain to see what color is left behind. </li></ul>
  22. 22. 5 major properties <ul><li>5) Cleavage/ Fracture- this is the way a mineral breaks. </li></ul><ul><li>Minerals that break along a smooth flat surface have cleavage. </li></ul>
  23. 23. 5 major properties <ul><li>Cleavage/ Fracture- Minerals that break unevenly, or with rough jagged surfaces have fracture. </li></ul>
  24. 24. Uses of Minerals <ul><li>Gems - Gems are highly prized minerals due to their rareness and beauty. </li></ul><ul><li>They are clearer brighter and more colorful then common minerals. </li></ul><ul><li>Gems always come from other minerals. </li></ul><ul><li>Ex: Amethyst is a gem that comes from Quartz. Because it has less iron in it than quartz does it has a beautiful purple color. </li></ul>
  25. 25. Useful Gems <ul><li>Some gems are very useful like diamonds. </li></ul><ul><li>They are not only used to make beautiful jewelry but since they are the hardest mineral on Earth they are also used for cutting tools like saw blades. </li></ul><ul><li>Rubies are used to create lasers. </li></ul><ul><li>Quartz is used in watches and clocks. </li></ul>
  26. 26. Test in 1 Week!!!!