1. Sandstone: Formed from cemented sand grains. You might see this in your backyard if you live in a sandy area.

2. Limestone: Formed from the skeletons and shells of marine organisms. Limestone is used to make cement and is found in caves.

3. Shale: Formed from compacted clay. Shale is often found in layers and can split easily.

4. Coal: Formed from compacted plant matter. Coal is a fossil fuel used for energy.