1. How Are Minerals Identified?
Minerals are identified by their properties.
Color
Luster
Hardness
Streak
Density
Crystal Shape
Cleavage and Fracture
Special Properties, such as magnetism, smell, taste and radioactivity

2. Color Usually the first and most easily observed
Not a reliable way to identify a mineral
- Some minerals are the same color as others
- Some minerals can have many colors
ROSE QUARTZ
QUARTZ
SMOKY QUARTZ

3. Luster General appearance of a mineral surface in reflected light
Glassy-Obsidian

4. Examples of luster Metallic Vitreous: similar to glass
Resinous: resembles the way plastic reflects light
Pearly: resembles the way pearls shine
Greasy: resembles the way petroleum jelly or a greasy surface reflects light
Silky: resembles the way silk reflects light
Earthy: dull, may be rough or dusty
Waxy
Adamantine: resembles the way a diamond shines
Fibrous – looks like fibers
Pitchy – looks like tar

5. Hardness Resistance to scratching by different items; “scratchability”
Mohs Hardness Scale is used to determine the hardness of minerals by comparing them to substances of known hardness:
< 2 fingernail
3 penny
~ 5 Steel of a pocket knife
5.5 Window Glass
6.6 Steel of a file
7 Quartz crystal

6. Mohs Mineral Hardness Scale
1) Talc
2) Gypsum
3) Calcite
4) Flourite
5) Apatite
6) Feldspar
7) Quartz
8) Topaz
9) Corundum
10) Diamond
Softest 1 9 5 2 6 10 3 7
Hardest 4 8

7. Streak The color of a finely powdered mineral
Determined by rubbing the mineral on a piece of unglazed porcelain (streak plate)

8. Density
The amount of matter in a given space
Specific Gravity is the comparison of a substance’s density to the density of water

9. Crystal Shape
Minerals have a characteristic crystal shape resulting from the atomic packing of the atoms when the mineral is forming

10. Cleavage and Fracture
Cleavage is the tendency of a mineral to split or crack along parallel or flat planes.
Fracture occurs when a mineral breaks at random lines instead of at consistent cleavage planes.
BIOTITE
QUARTZ
Obsidian
1 Direction of Cleavage
No Cleavage
Conchoidal Fracture

11. Fracture

12. Special Properties Magnetism (Magnetite)
Glowing under ultraviolet light (Fluorite)
Taste (Halite)
Smell (Sulfur)
Reaction to HCl (Calcite)
Double refractive - a thin, clear piece of calcite placed over an image will cause a double image
Radioactivity - minerals containing radium or uranium can be detected by a Geiger counter

13. Economic Importance of Minerals
Minerals are in many things we see and use everyday such as; bricks, glass, cement, plaster, iron, gold

14. Every American Requires 40,000 Pounds of New Minerals per Year
At this level of consumption the average newborn infant will need a lifetime supply of:
- 795 lbs of lead (car batteries, electric components)
- 757 lbs of zinc (to make brass, rubber, paints)
lbs of copper (electrical motors, wirings
lbs aluminum (soda cans, aircraft)
- 32,700 lbs of iron (kitchen utensils, automobiles, buildings)
- 28,213 lbs of salt (cooking, detergents)
- 1,238,101 lbs of stone, sand, gravel, cement (roads, homes)