Igneous
Igneous rocks are formed from melted rock that has cooled and solidified. When magma (molten rock) cools slowly, usually at depths of thousands of feet, crystals grow from the molten liquid, and a coarse-grained rock forms. When magma cools rapidly, usually at or near the Earth's surface, the crystals are extremely small, and a fine-grained rock results.
Granite
Sedimentary
Sedimentary rocks are formed at the surface of the Earth, either in water or on land. They are layered accumulations of sediments made of rock fragments, minerals, or organic material. Most sedimentary rocks become cemented together by minerals and chemicals.
Black Shale
Metamorphic
Sometimes rocks are subjected to pressures so intense or heat so high that they are completely changed. They become metamorphic rocks, which form while deeply buried within the Earth's crust. The process of metamorphism does not melt the rocks, but instead transforms them into denser, more compact rocks. New minerals are created either by rearrangement of mineral components or by reactions with fluids that enter the rocks. Pressure or temperature can even change previously metamorphosed rocks into new types.
