1. Minerals of the Earth

2. What is a mineral?
What objects in this classroom are considered minerals?
Mineral: naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure.
Minerals occur naturally and all minerals are inorganic (never alive)
All minerals are solids (definite shape and volume)
The chemical composition of a mineral is specific to that type of mineral
Atoms arranged in geometric pattern that repeat; gives the crystalline structure of the mineral
6 major crystal systems: Table 4-1
Well defined crystals= formed in open space
Density and hardness make each mineral unique

3. Minerals from Magma
Magma: molten material found beneath the Earth’s surface
Magma forced upward (density differences) where the magma cools; compounds interact chemically to form minerals
Type and amount of elements found determine which minerals will form
Rate of cooling determines the size of mineral crystals
Magma cools slow: large crystals
Magma cools quickly: small crystals form

4. Minerals from Solution
Water in a solution can dissolve only so much of a solid before the water becomes saturated.
If solution becomes supersaturated (overfilled) with another substance, mineral crystals begin to form
Can also form when elements dissolve in supersaturated solution
Ex: Gypsum deposits form from evaporated water

6. Mineral Groups
Silicates: minerals that contain silicon and oxygen, and usually one or more other elements; 96% of minerals found in Earth’s crust EX: feldspar and quartz (most common minerals); unique structure accounts for the diversity of silicates
Carbonates: minerals composed of one or more metallic elements with the carbonate compound EX: calcite, dolomite, and rhodochrosite; primary minerals found in rocks such as limestone and marble; distinct colorations
Oxides: compounds of oxygen and a metal; hematite and magnetite are iron oxides (good source of iron); uraninite valuable for source of uranium (generates nuclear power)

8. Mineral Identification
Hardness: most useful test; measure of how easily a mineral can be scratched. Measured using Mohs scale of hardness; determined by the arrangement of a mineral’s atoms.
Cleavage & Fracture: determined by atomic arrangement; cleavage: mineral that splits relatively easily along one or more planes fracture: minerals that break with rough or jagged edges
Density & Specific Gravity: reflects the atomic weight and structure of a mineral; useful identification tool; sometimes too small to tell differences;
Color: caused by trace elements or compounds; least reliable clues to a minerals identity
Luster: way a mineral reflects light from its surface; either metallic (shiny surfaces) or nonmetallic (do not shine like metals); caused by differences in chemical composition
Texture: how feels to touch; often used in combination with other tests; smooth, rough, ragged, greasy, soapy or glassy.
Streak: the color of a mineral when it is broken up and powdered; not always the same as the mineral color. Rarely changes; cant be used to identify all minerals (if harder than a porcelain plate)

9. Table 4-1

10. Special Properties
Double refraction: refraction of a single ray of light into two rays creating two images (due to arrangement of atoms)
Chemical composition: calcite fizzes when in contact with HCl; releases CO2 in form of bubbling gas
Special properties of specific minerals aid in identification

11. Mineral Uses
Ores: contains a useful substance that can be mined at a profit
EX: hematite is useful ore that contains element iron
ANY ITEMS MADE OF IRON IN THIS ROOM? ALUMINUM?
Mines: ores located deep within Earth’s crust removed by underground mining.
Necessary to get rid of the waste material before the ore can be used
This process can be very costly and harmful to the environment

12. Gems
These are valuable minerals that are prized for their rarity and beauty
Rubies, emeralds, and diamonds (rubies & emeralds more valuable)
Used for jewelry