ROCK FORMING MINERALS ABOUT 20 minerals make up most of the rocks in the Earths crust.

ROCK FORMING MINERALS• ABOUT 20 minerals make – up most

of the rocks in the Earth’s crust.

HOW GEOLOGIST CLASSIFY ROCKSIn 3 CATEGORIES

MINERAL COMPOSITIO

N

COLOR TEXTURE

The mixture of minerals &

other materials that make a

rock

Gives clues about what

minerals are in the rock

Look & feel of a

rock

Grain shape

Grain

size

Grain Pattern

MINERAL COMPOSITION

COLOR

GRAIN SIZEThe size of the

mineral visible in the rock

GRAIN SHAPEThe shape of the mineral visible in

the rock

GRAIN PATTERN The design of the mineral visible in

the rock

Jagged: Breccia

Rounded: Conglomerate

Course Grain:Granite

Fine Grained: Basalt

Banded Non - Banded

ORIGIN