Igneous Rocks

Rock A group of minerals bound together in some way Minerals= ingredients Rock= cookie

2 Kinds of Igneous Rocks

2 Kinds of Igneous Rocks Intrusive/ Plutonic (within): Formed underground from magma Usually coarse-grained texture  Large crystals Slow cooling process Extrusive/ Volcanic (outward/exit): Formed on surface from lava, dust, ash Usually fine-grained texture  Small crystals Rapid cooling process

2 Kinds of Magma/Lava Felsic: Light in color Rich in: Al, K Usually contains feldspar, quartz, muscovite Ex: Granite, Rhyolite Mafic: Dark in color Rich in: Fe, Mg Contains olivine, feldspar, biotite Ex: Gabbro, Basalt

Texture  *DRAW IN NB*  Crystals big enough to see with eyes Coarse-grained: Crystals big enough to see with eyes Magma cools slowly underground  Crystals have time to grow (more time = larger crystals) Fine-grained: Crystals are small, instruments are needed to see them Magma/lava cools rapidly on surface  Crystals have no time to grow (less time = smaller crystals)  *DRAW IN NB* 

Texture Porphyritic: Coarse-grained crystals surrounded by fine-grained crystals Magma cools slowly underground, then suddenly begins cooling rapidly

Summary What are the two types of igneous rocks How do you know an igneous sample is mafic or felsic? What does the texture of an igneous rock tell you?