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Minerals

Minerals. How do we use Earth Materials?. Earth Materials : minerals, rocks, and mineral resources (95% to 100% of objects you use). What is a mineral?. Mineral : a naturally occurring, inorganic, crystalline solid that has a definite chemical composition.

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Minerals

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  1. Minerals

  2. How do we use Earth Materials? • Earth Materials: minerals, rocks, and mineral resources (95% to 100% of objects you use)

  3. What is a mineral? • Mineral: a naturally occurring, inorganic, crystalline solid that has a definite chemical composition. 1. Naturally Occurring: a mineral must be formed by nature and not made by people.

  4. What is a mineral? 2. Inorganic: a mineral CANNOT form from materials that were once part of a living thing.

  5. What is a mineral? 3. Crystalline solid: a mineral is always a solid, with its own unique crystal structure.

  6. What is a mineral? 4. Definite Chemical Composition: a mineral always contains certain elements in definite proportions. Gold Quartz

  7. Mineral or NOT? • Rock salt • AKA Halite • NaCl

  8. Mineral or NOT? • Beach sand • AKA tiny pieces of Quartz • SiO2 • Crystal shape is a pyramid

  9. Mineral or NOT? • Snow • Occurs naturally

  10. Mineral or NOT? • An ice cube

  11. How are Minerals Related to Rocks? • A rock is any naturally formed solid that is part of Earth or any other celestial object. • Organic or glassy rocks are NOT minerals.

  12. How are Minerals Related to Rocks? • There is only a small number of minerals commonly found in rocks.

  13. Mineral Crystal Structure • A mineral’s atomic arrangement is responsible for many of its chemical and physical properties.

  14. Silicate Minerals • What two elements, by mass, make up the greatest percentage of the Earth’s crust?

  15. These two elements combine to form compounds called silicates. The mineral Quartz is a type of silicate (SiO4)

  16. They (Silica and Oxygen) combine in a specific structure called a: Silicon-oxygen tetrahedron.

  17. Draw this structure below. O Si O O O

  18. Mineral Formation Minerals can form in TWO ways: • Crystallization of molten material • Crystallization of materials dissolved in water. Salt on a stone of the Dead Sea, Israel

  19. Massive beams of selenite dwarf human explorers in Mexico's Cave of Crystals, deep below the Chihuahuan Desert. Formed over millennia, these crystals are among the largest yet discovered on Earth

  20. Mineral Identification • Each mineral has unique properties that can be used to identify it. 1. Color: the easiest test to do on a mineral, but the least reliable. Rose Quartz Citrine Amethyst

  21. Quartz Halite Calcite Corundum

  22. Mineral Identification 2. Streak: the color of the powdered mineral • Obtained by rubbing the unknown mineral on a streak plate (porcelain tile). The mineral Hematite ALWAYS has a red streak

  23. One way to tell Fool’s Gold apart from real Gold is by their STREAK. Real gold has a golden streak Pyrite has a black or dark green streak

  24. Mineral Identification 3. Luster: The shine from an unweathered mineral’s surface • Metallic – shines like a polished piece of metal. • Non-metallic– does NOT shine like a metal.

  25. Metallic luster in Galena Metallic luster in Pyrite Pearly luster in Muscovite Earthy luster in Hematite Glassy luster in Quartz

  26. Mineral Identification 4. Hardness: a mineral’s resistance to scratching • The hardness of some common items: • Fingernail – 2.5 • A Penny – 3.5 • Glass – 5.5 • A Streak Plate – 6.5

  27. Mineral Identification 5. Specific Gravity: the density of a mineral compared to the density of water. The mineral Galena has a high specific gravity

  28. Mineral Identification • Cleavage: the tendency of a mineral to break along the zones of weakness • Minerals can have one, two, or several cleavage planes Feldspar has TWO cleavage planes Mica has ONE cleavage plane Halite (salt) has THREE cleavage planes

  29. Mineral Identification • Fracture: a mineral may break along uneven surfaces. • Mineral has no preferred zones of weakness. Splintery fracture in Hornblende Conchoidal fracture in Quartz

  30. Mineral Identification 8. Crystal Structure: orderly arrangement of the atoms in the mineral • The geometric shape of a mineral can reflect its crystal structure. Herkimer Diamonds are quartz crystals that have a unique 18-sided geometric shape.

  31. Other Ways to Identify Minerals • Acid – Calcite will fizz in weak hydrochloric acid (HCl) • Magnetism – Magnetite will pick up paper clips / staples. • Taste – Halite is rock salt and will taste salty. • Fluorescence – some minerals (mostly forms of calcite) will glow in fluorescent colors under a black (UV) light. • Double refraction – some clear forms of calcite will make a double image of words.

  32. Fluorescence of Minerals

  33. Double Refraction

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