A mine can be on the surface of the earth or underground. Placer mining is done on the surface to mine gold or diamonds that are washed out of the ground by a river or stream. Metals such as iron and copper and minerals such as coal can be mined in an open-pit or a strip mine, which is basically a huge hole dug out of the surface. These mines can damage the landscape and leave holes in the earth hundreds of feet deep. Underground mines are dug to mine deposits of minerals such as coal that are located deep in the earth. The miners reach these deposits through vertical shafts and horizontal tunnels.