Question: what are the two groups of chemical sedimentary rocks?
Answer: Chemical - precipitate from solution (e.g., limestone); most important constituents are calcite, dolomite, chalcedony (SiO2), gypsum, and halite. Chemical sedimentary rocks can be further divided as to: inorganic (e.g., limestone, rock salt, dolomite) organic (e.g., limestone or coal).