Quartz, pyrite, and sphalerite are often found together in mineral deposits. Quartz is a hard, clear or milky mineral that usually forms the background of these deposits. Pyrite, also called “fool’s gold,” is a shiny, yellow mineral made of iron and sulfur. Sphalerite, a mineral that contains zinc, usually appears as brown, yellow, or reddish crystals. Together, these minerals can indicate a sulfur-rich environment, with sphalerite being important for extracting zinc.