There are three main types of rocks: sedimentary, igneous, and metamorphic. Sedimentary rocks form from the accumulation of sediments or organic matter. Igneous rocks form from the cooling of molten rock material either below or above the Earth's surface. Metamorphic rocks were once sedimentary or igneous rocks that were altered by heat, pressure, and chemical processes underground.

2. Listen up... a WORD about Geology and the rock cycle .

12. Metamorphic Rock - Foliated Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains. It typically contains abundant quartz or feldspar minerals.

13. Metamorphic Rock - Non-Foliated Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone. It is composed primarily of calcium carbonate.

14. The Rock Cycle