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
