Igneous RocksIgneous Rocks

What are they?What are they?

Rock made from cooled LAVA or Rock made from cooled LAVA or MAGMA.MAGMA.

ClassificationClassification

Igneous Rock is classified in 3 Igneous Rock is classified in 3 ways…ways…

1.1. TextureTexture

2.2. Origin (where it formed)Origin (where it formed)

3.3. Mineral CompositionMineral Composition

TextureTexture

Coarse Grained = large grains, Coarse Grained = large grains, cooled slowlycooled slowly

Fine Grained = small grains, cooled Fine Grained = small grains, cooled fastfast

Porphyritic = small AND large grains Porphyritic = small AND large grains (resembles jello w/fruit in it)(resembles jello w/fruit in it)

Course Grained

Granite = Intrusive Igneous rock

Fine Grained

Basalt = Extrusive Igneous rock

Porphyritic Texture

Porphyritic Granite

OriginOrigin

Intrusive – formed UNDERGROUND. Intrusive – formed UNDERGROUND. It cools slowly so it will have large It cools slowly so it will have large grains.grains.

Extrusive – formed ABOVE GROUND. Extrusive – formed ABOVE GROUND. It cools fast so it has small grains.It cools fast so it has small grains.

Mineral CompositionMineral Composition

How much silica is in the How much silica is in the magma/lava?magma/lava?– High silica content = light colored = High silica content = light colored =

MaficMafic– Low silica content = dark colored = Low silica content = dark colored =

FelsicFelsic

High Silica Content Low Silica Content

Mafic Igneous Rock Felsic Igneous Rock