Igneous Rocks
What are they? Rock made from cooled LAVA or MAGMA.
Classification Igneous Rock is classified in 3 ways… Texture Origin (where it formed) Mineral Composition
Texture Coarse Grained = large grains, cooled slowly Fine Grained = small grains, cooled fast Porphyritic = small AND large grains (resembles jello w/fruit in it)
Course Grained Granite = Intrusive Igneous rock Fine Grained Basalt = Extrusive Igneous rock Porphyritic Texture Porphyritic Granite
Origin Intrusive – formed UNDERGROUND. It cools slowly so it will have large grains. Extrusive – formed ABOVE GROUND. It cools fast so it has small grains.
Mineral Composition How much silica is in the magma/lava? High silica content = light colored = Mafic Low silica content = dark colored = Felsic High Silica Content Low Silica Content Mafic Igneous Rock Felsic Igneous Rock