Some minerals, given time and circumstance, form solid deposits. These solid mineral deposits are known as rock.
Pressure, temperature, erosion, and friction are forces that effect the formation of rocks. The rock formation process allows geologists to classify rocks into three groups: sedimentary, igneous, and metamorphic.
1. Breccia
2. Coal
3. Limestone
4. Phyllite
5. Marble
6. Pumice
7. Obsidian
8. Tuff
