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Types of Rocks & Fossils

Rocks form from a group of minerals. There are three types of rocks: sedimentary, igneous and metamorphic. These types are classified by how they form. Fossils are found in sedimentary rocks and are the remains of organisms. Fossils are classified by how they have geologically formed.

Sedimentary Rocks
- Sedimentary rocks form from sediments that have been deposited and cemented together. Fossils are only found in sedimentary rocks. Rock salt, sandstone and shale are examples of sedimentary rocks.
Igneous Rocks
- Igneous rocks form from the cooling of magma or lava. The texture of igneous rocks is based on the speed of cooling. The slower an igneous rock cools, the larger the crystals that form. Granite, basalt and obsidian are examples of igneous rocks.
Metamorphic Rocks
- Metamorphic rocks form from a change in crystallization when rocks are exposed to high temperatures and pressures. Slate and marble are examples of metamorphic rocks.
Body Fossils
- Body fossils are the remains of the actual organism. Body fossils can be mold fossils, cast fossils, premineralized fossils or petrified fossils.
Trace Fossils
- Trace fossils are fossils that show the activity of the organism. Footprints, burrows and coprolites are examples of trace fossils.

Rocks & Minerals