1. Minerals

2. Minerals: the building blocks of rocks
Definition of a Mineral:
naturally occurring
inorganic (nonliving)
solid
characteristic crystalline structure
definite chemical composition

3. How do we identify minerals?
Physical properties:
Hardness
Luster
Streak
Cleavage / Fracture
Color

4. Physical Properties of Minerals
Hardness:
How easy it is to scratch a mineral
Mohs Scale of Hardness
relative scale
consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

5. Mohs Scale of Hardness Hardest (10) – Diamond Softest (1) – Talc
Common objects:
- Fingernail (2.5)
- Copper penny (3.0)
- Steel nail (5.0)
- Glass (5.5)
- Streak plate (7.5)

6. Physical Properties of Minerals
Luster:
How a mineral surface reflects light
Two major types:
Metallic luster
Non-metallic luster
Metallic
example:
Galena
Non-metallic
example:
Orthoclase

7. Physical Properties of Minerals
Streak -
color of a mineral in powdered form
Obtained by scratching a mineral on a piece of unglazed porcelain.
Example:
Hematite

8. Physical Properties of Minerals
Cleavage - Some minerals split along flat surfaces when struck hard--this is called mineral cleavage

9. Physical Properties of Minerals
Fracture: Other minerals break unevenly along rough or curved surfaces--this is called fracture
Quartz

10. Physical Properties of Minerals
Color:
Most obvious, but often misleading
Different colors may result from impurities
Example:
Quartz

11. Mineral Groups Rock-forming minerals
~30 common minerals make up most rocks in Earth’s crust