Three Types of Rock

Part of Hall of Planet Earth.

Three Types of Rock
There are three kinds of rock: igneous, sedimentary, and metamorphic.

Igneous rocks form when molten rock (magma or lava) cools and solidifies. Sedimentary rocks originate when particles settle out of water or air, or by precipitation of minerals from water. They accumulate in layers. Metamorphic rocks result when existing rocks are changed by heat, pressure, or reactive fluids, such as hot, mineral-laden water. Most rocks are made of minerals containing silicon and oxygen, the most abundant elements in the Earth’s crust.

Limestone
Limestone is one of the most widespread sedimentary rocks. Many organisms, from corals to microscopic foraminifera, grow shells composed of carbonates. Most limestone forms when these organisms die and their carbonate shells accumulate in shallow seas.
Large piece of layered shale rock on display.
two rock types: limestone (left); sandstone (right)
Manhattan schist
Slate
In the Museum’s Hall of Planet Earth, a specimen of gneiss. The rock is mottled with pink, black, and gray-colored mineral content throughout.
Granite Pegmatite
AMNH/R.Mickens
Diabase
Diorite

In This Section

Exhibit Igneous Rocks Igneous rocks solidify from molten rock (called magma within the Earth and lava on the surface). Exhibit Sedimentary Rocks Sedimentary rocks are layered. Exhibit Metamorphic Rocks Metamorphic rocks form when sedimentary, igneous, or pre-existing metamorphic rocks are changed by environmental factors.