1. 5.2 – Classifying Igneous Rocks

2. Mineral Composition There are 3 main groups of igneous rocks
Felsic, mafic, and intermediate
Felsic rocks are light-colored, have high silica contents, and contain feldspars and quartz
Mafic rocks are dark-colored, have high silica contents, and are rich in iron and magnesium

3. Ultramafic Rocks
These contain low silica content and high levels of iron and magnesium

4. Porphyritic Texture
A porphyritic texture is characterized by large, well formed crystals surrounded by finer-grained crystals of the same mineral or different minerals
These textures indicate a complex cooling history where slowly cooling magma suddenly began cooling rapidly

5. Igneous Rocks as Resources
They are useful for building materials because of their strength and resistance to weathering

10. Ore Deposits
Veins are fluid left during magma crystallization contains high levels of silica and water
This fluid also contains any leftover elements that were not incorporated into the common igneous rock (gold, silver, lead and copper)