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Properties of Minerals

Explore the fascinating world of minerals and how geologists use their characteristics to distinguish one from another. Learn about mineral formation, physical properties such as luster, hardness, streak, cleavage, and color, as well as the unique attributes that make each mineral distinct. Delve into the realm of gems and understand the value they hold in the world of geology. Enhance your knowledge with valuable insights into the intriguing world of minerals and gems.

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Properties of Minerals

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  1. Properties of Minerals Geologists use characteristics to tell one mineral from another

  2. What is a mineral? • S olid • N aturally Occuring • I Inorganic • F ixed Composition • C Crystal Form

  3. Groups of Minerals • Minerals are grouped by the elements they are made of. Beryl (Emerald) Calcite Amethyst

  4. MICA Quartz

  5. Silver Copper Diamond Gold Iron Ruby

  6. Calcite with Duftite inclusions

  7. BariteBaSo4 Barite on CalciteBaSo4 / CaCO3

  8. How do minerals form? • 1) Cooling of magma (hot, liquid rock and minerals inside the earth (from the mantle)) • Fast Cooling = No Crystals (mineraloids) • Medium Cooling = small crystals • Slow Cooling = large crystals

  9. How do minerals form? • 2) Elements dissolved in liquids (usually water)

  10. Mineral properties • Color • Luster • Habit (Shape) • Cleavage & Fracture • Streak • Hardness • Other

  11. Metallic Non-metallic Luster: How minerals reflect light

  12. Physical Properties of Minerals(can be used to identify the mineral) Luster • Surface reflection • metallic = shiny like metal • non-metallic = dull, non-shiny surface Pyrite has a metallic luster Calcite has a non-metallic luster

  13. Pyrite has metallic luster

  14. Quartz has nonmetallic luster

  15. Physical Properties of Minerals(can be used to identify the mineral) Hardness • How easily a mineral scratches materials • Mohs Hardness Scale • Scale from 1 (softest) to 10 (hardest) • Test by seeing if the mineral can scratch different objects (like human fingernail, copper, penny, glass, steel file)

  16. Gypsum is soft, it can be scratched by a fingernail.

  17. Calcite is soft, but a little harder because it cannot be scratched by a fingernail, but it can be scratched by a penny.

  18. Fluorite is harder. It can be scratched by a nail, but not a penny or fingernail.

  19. Diamonds are the hardest mineral, so it scratches every mineral.

  20. Mineral Habit (Shape) Shape a mineral takes if grown unimpeded

  21. Physical Properties of Minerals(can be used to identify the mineral) Streak • The color of the powdered form of the mineral • The color of the streak can be different than the mineral • Minerals must be softer than the streak plate

  22. Streak • Red chalk on a chalk board makes red marks. White chalk makes white marks. • Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.

  23. Gold • When gold is run across a streak plate it makes a yellowish-gold color. • That makes sense.

  24. Pyrite or “Fool’s Gold” • When pyrite is run across a streak plate, it has a black or dark green streak. • Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.

  25. Hematite • Hematite’s color is grey, but its streak is red. • Hema means blood. • The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.

  26. Streak…can help identify quartz BUT... http://www.childrensmuseum.org/geomysteries/cube/b3.html

  27. Cleavage • Not all minerals have cleavage. • Some minerals split easily along a flat surface. • The number of lines that are created when a mineral is split will be the number of cleavage lines.

  28. Physical Properties of Minerals(can be used to identify the mineral) Cleavage & Fracture • The way the mineral breaks • Cleavage—minerals break along smooth, flat surfaces and every fragment has the same general shape • Fracture—minerals that break at random with rough or jagged edges

  29. Fracture breaks irregularly in all different shapes and sizes. QUARTZ

  30. Physical Properties of Minerals(can be used to identify the mineral) Color • Can be misleading • Can vary with the type of impurities

  31. Color: Not mineral specific

  32. One mineral property we will use… is COLOR However...

  33. A mineral can be many different colors. Below is Mica.

  34. Many minerals can be the same color. Below are gold colored minerals. Which one is gold?

  35. The answer… None of them were real gold.

  36. Physical Properties of Minerals(can be used to identify the mineral) Other Properties • Specific gravity (*excellent clue to mineral’s identity) Specific Gravity • Attraction to magnets • Bending of light • Reaction with hydrochloric acid • Smell & taste (Never taste anything in the our school lab.)

  37. Just like with people… Outside color does not tell you much about the important characteristics.

  38. What is a gem? • A Mineral OR Rock that has value • Rare ! • Sometimes polishing or cutting will add value

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