Dolostone is a sedimentary rock that contains a high percentage of the mineral dolomite. It is usually referred to as dolomite rock. In old U.S.G.S. publications it was referred to as magnesian limestone. Typically, dolostone and impure limestone occur together, along with abundant chert and siltstone layers. Most dolostone formed as a magnesium replacement of limestone or lime mud prior to lithification. It is resistant to erosion in dry climates and can either contain bedded layers or be unbedded. The unbedded sections are a result of bioturbation. In humid climates, dolostone frequently develops a karst terrain surface with abundant underground caverns. It is less soluble than limestone in weakly acidic groundwater, but it can still develop solution features over time.