Special Sedimentary Rocks
There are many types of sedimentary rocks. The sedimentary rocks listed here are interesting or have economic importance.
• Travertine is a calcite-rich rock found in cave formations. Tufa is a porous rock formed near calcareous springs.
Stalactites (Photograph by Parvinder Sethi)
Travertine is the rock that makes up most cave deposits, including the stalactites in this picture. Deposits that form this way are also called dripstone.
• Chalk is a kind of limestone made of a mixture of calcite-rich and silica-rich organic remains.
• Coquina is a kind of limestone made of weakly cemented, broken animal shells. Coquinas form in beach and shallow water environments where waves break apart animal shells.
Coquina (Photograph by Parvinder Sethi)
• Coal is a biochemical sedimentary rock made up of compacted ancient vegetation formed in swamps.
Coal (Photograph by Parvinder Sethi)