 |
| Granite is the most common and best known igneous rock. Granite forms when magma cools slowly, deep below the Earth's surface, giving crystals a long time to grow. Granite is generally pink or white, and is composed primarily of quartz and feldspar with lesser amounts of hornblende and mica. |
 |
| Sandstone is a sedimentary rock that is comprised entirely of quartz grains. the quartz grains accumulated and were deposited as sediments by the action of wind and water. Sandstone can be many colors and commonly exhibits layering or banding resulting from successive periods of deposition. |
 |
| Gneiss is a metamorphic rock that shows banding and foliation typical of most metamorphic rocks. In many cases, it forms as the result of metamorphism of igneous rocks such as granite or diorite. Gneiss, therefore contains quartz, feldspar, and micas that have segregated into bands during the process of metamorphism. |
|
|
 |