RocksRocksEarth’s crust is made of Earth’s crust is made of rock.rock.Rocks are Rocks are mixtures mixtures of of mineralsminerals and sometimes and sometimes other materialsother materials..

When studying a When studying a rock rock samplesample, geologists observe , geologists observe the rock’s:the rock’s:ColorColorTextureTextureChemical compositionChemical composition

Most rocks are made up of Most rocks are made up of grainsgrains, , particles of particles of mineralsminerals, or other , or other rocks.rocks.

TextureTexture is the look that results is the look that results from:from:

SizeSizeShapeShapePatternPattern of rock’s of rock’s grainsgrains

CoarseCoarse-grained---grained--large/easy to see.large/easy to see.FineFine-grained – -grained – small, even small, even microscopic.microscopic.

Grains in rock often form a Grains in rock often form a patternpattern..

FlatFlat layers layers ((stratastrata))

Wavy, Wavy, swirlingswirling patternspatterns

Rows of Rows of beadsbeads

RandomRandom or no pattern or no pattern

Some rocks have Some rocks have NO grainNO grain, , because they cooled too because they cooled too quickly when they quickly when they formedformed..

There are There are 33 groups of groups of rocks:rocks:

IgneousIgneousMetamorphicMetamorphicSedimentarySedimentary

Igneous RocksIgneous Rocks

Formed from the cooling of Formed from the cooling of moltenmolten (melted) (melted) rockrock..

Examples:Examples:

pumice, granite, basaltpumice, granite, basalt

Sedimentary RocksSedimentary RocksFormed when particles of other rocks, plants, or animals are cemented together.Examples:

Sandstone, breccia, siltstone

Formed when existing rock is changed by heat, pressure, or chemical reactions.Examples:

gneiss, schist, phyllite

Metamorphic RocksMetamorphic Rocks

The Rock CycleThe Rock Cycle