Review: Minerals

T/F Rocks are found inside mineralsT/F Minerals are always solid

T/F Rocks always have a crystal structureT/F There are 4 characteristics that make up

minerals

5 Physical Properties of Minerals

• Color

• Streak

• Luster

• Cleavage

• Hardness

Color

• Most minerals have a limited color range– Least accurate way to identify a mineral

– Different things cause color to vary• Being at/near Earth’s surface• Defects

Streak

• The color of the powder left behind when the mineral is scraped across a surface– This method is much better than relying on

color– Wulfenite and Rubies are both red, but they

have different hardness

Luster

• How it shines:– Metallic

• Looks like it’s made of metal

– Non-metallic• Does not look like a metal

Cleavage and Fracture

• How it breaks gives us more information than color and luster

• Fracture– Breaks into irregular pieces– Bonds are equal in all directions

• Cleavage– Breaks along flat surfaces– Weaker bonds– Broken surfaces that are smooth

Hardness

• How resistant the mineral is to being scratched

• We use Mohs scale that is listed to the side

HARDNESS SCALE

INDEX MINER

AL

COMMON OBJECTS

1 Talc

2 Gypsum Fingernail 2.5

3 Calcite

4 Fluorite Copper Penny 3

5 Apatite

6 Orthoclase

Glass 5.5

Steel Knife 6.5

7 Quartz

8 Topaz

9 Corundum

10 Diamond

More info on Hardness

• The Moh’s Hardness Scale ranks the order of hardness. For example, your fingernail can scratch the minerals talc and gypsum because those minerals have a hardness of 2 or lower. A copper penny can scratch calcite, gypsum, and talc.

• Any mineral can scratch glass as long as it has a

hardness > (greater than) 6.