1. Minerals Mrs. Nell 6th General Science Chapter 15 (Section 1)

2. What is a Mineral? Mineral: inorganic solid material found in nature Same chemical makeup Orderly pattern of atoms Building blocks of all rocks Over 4000 minerals identified Form from melted rock or from solutions that evaporate Fluorite

3. How Minerals Form  We can get a clue how a mineral formed by how it looks… Look at size of grain or crystal presence of layers, texture the way mineral grains fit together like a puzzle- cooled from magma layers of different minerals- probably formed by evaporation

4. Cooled From Magma There are two main ways that new crystals of minerals grow. Some minerals form when molten rock, called magma below the planet’s surface and lava above, cools and atoms bond together into mineral crystals.

5. Minerals from Evaporation Other minerals form when water that has atoms of dissolved elements in it, evaporates away. The atoms get very close to each other and may bond together to form solid minerals. When ancient seas slowly evaporated, minerals like halite, gypsum, and calcite formed. Halite GypsumCalcite

6. Properties of Minerals Properties can be used to help identify minerals… 1)Crystals 2)Cleavage/Fracture 3)Streak 4)Luster 5)Hardness 6)Other Properties

7. 1) Crystals 1)Crystals- atoms of minerals are arranged in repeating patterns Smooth surfaces Sharp edges Points

8. 2) Cleavage / Fracture Can study the way mineral breaks… Splits with smooth, regular edges and surfaces- said to have cleavage (ex- mica)  reaks into pieces with jagged/rough edges (ex- quartz, native copper)- said to fracture

9. 3) Streak Color can fool you (ex- pyrite) Streak test will help identify even if It looks like a different mineral Scratching mineral sample across unglazed white tile (streak plate) produces streak of color (not always same as mineral itself in color) Pyrite- greenish-black or brownish-black streak Gold- yellow streak

10. 4) Luster Luster- how light is reflected from mineral’s surface Shines like mineral- metallic luster Nonmetallic minerals- pearly, glassy, dull, earthy luster

11. Mineral Luster Metallic ChalcocitePyriteGalena

12. Mineral Luster Non-metallic Pearly MicaTalc Dolomite

13. Mineral Luster Glassy Many samples with non-metallic luster are shiny, but it is the shine of glass rather than metal. Calcite Garnet Aragonite Amethyst

14. Mineral Luster Dull or Earthy Earthy luster is applied to samples that look powdery or soil- like. KaoliniteLimoniteChrysocolla

15. 5) Hardness 1822- Austrian Friedrich Mohs developed Mohs scale- way to classify minerals from 1 (softest) to 10 (hardest) You can use a penny, nail, or glass plate with smooth edges to test hardness. Can the mineral scratch a penny? Glass?

16. 6) Other Properties Magnetism (ex- magnetite) Calcite- fizzes when in contact with an acid like vinegar Fluorite glows under ultraviolet light Halite or rock salt tastes salty Sulfur has an unusual odor Calcite in vinegar

17. Common Minerals In rocks, the most common minerals are: 1.Quartz 2.Feldspar 3.Biotite 4.Mica 5.Calcite 6.Gypsum 7.Hornblende 8.Fluorite 9.Augite 10.Hematite 1 2 3 4 5 6 7 8 9 10

18. Gems Most other minerals (diamonds, emeralds, etc.) are rare Gems: minerals that are rare and can be cut and polished, giving a beautiful appearance –Must be clear with no blemishes/cracks –Must have a beautiful color

19. Ores Ores: a mineral that contains something that can be useful and sold for profit –Many metals come from ore –Iron: comes from mineral hematite –Lead (for batteries): produced from galena –Magnesium (in vitamins): comes from dolomite