in contrast to lithification, sedimentary rocks may also form from the precipitation of chemicals out of water. one common site of chemical sedimentation is desert lakes and lagoons. as evaporation occurs, the chemicals become increasingly concentrated in the water until they can no longer remain dissolved. they combine with one another, forming minerals such as calcite, gypsum, and salt. deposits formed from evaporation are called evaporites. chemical sedimentation also takes place in the ocean. biological processes play a crucial role in triggering this phenomenon. algae, coral, and invertebrate organisms all utilize calcium carbonate in constructing shells and reefs. when these organisms die, their carbonate hard parts accumulate on the sea floor to form limestone, one of the most common sedimentary rocks on earth. limestones vary greatly in appearance, from formations packed with large fossils to beds of chalk formed from the microscopic shells of plants and animals. life also contributes to the formation of sedimentary rocks other than limestone. in the cool, nutrient-rich water