Which statement does not describe one of the three main rock types?

• A. Igneous rocks form from cooling magma.
• B. Sedimentary rocks are formed by deposition and cementation.
• C. Metamorphic rocks are formed by heat and pressure.
• D. Peat is an example of an igneous rock.

Answer: (D)

Three main rock types are igneous, sedimentary, and metamorphic, and each is defined by how it forms. Igneous rocks come from cooling and solidifying molten material, either magma underground or lava on the surface. Sedimentary rocks form from pieces of other rocks or minerals that are deposited in layers, then compacted and often cemented together. Metamorphic rocks arise when existing rocks are altered by high heat and pressure, changing their minerals and structure.

Peat is not a rock at all; it’s organic material made from partially decomposed plant matter in wetlands. While peat can become coal under long-term pressure and heat, peat itself is not one of the three main rock types.