1. Igneous rocks Geology of National Parks and Monuments Prof. Kurt Friehauf

2. Basalt Mafic Fine-grained Black May have bubble holes like Swiss cheese Volcanic

3. Obsidian Volcanic glass Smooth with sharp edges Forms by quick cooling Can be mafic or felsic Volcanic

4. Pumice Froth of volcanic glass Light weight commonly floats in water Rough surface Forms as foam when lava slops around Volcanic

5. Scoria Mafic Red color due to oxidation of iron in mafic lava Rough, commonly bubbly Volcanic

6. Rhyolite Felsic Fine-grained Pink/tan/white color May contain pumice fragments Volcanic

7. Andesite Tuff Intermediate Fine-grained with chunks of other rocks Green/gray Forms by explosive eruption Volcanic

8. Granite Felsic Coarse-grained can see crystals Pink/tan/white with dark specks Plutonic (forms deep within earth, not volcanic)