Nonclastic Sedimentary Rocks

Nonclastic sedimentary rocks form from chemical reactions, chiefly in the ocean. Nonclastic and clastic sedimentary rocks are the only members of the rock family that contain fossils as well as indicators of the climate that was present when the rock was formed.

Nonclastic sedimentary rocks are named according to the mineral present.

Limestone = composed of the mineral calcite, may contain marine fossils; formed by precipitation from water
Rock salt = composed of the mineral halite (salt); formed by evaporation
Rock gypsum = composed of the mineral gypsum; formed by evaporation
Chert = composed of microscopic mineral grains of quartz; very hard with sharp edges

Mineral Photos courtesy of R.Weller/Cochise College