Indiana Caverns the calcium carbonate precipitates out of the water. The calcium carbonate, in the form of the mineral calcite, a solid, crystallizes onto the bottoms and sides of existing stalactites, stalagmites, helictites, and sheets of flowstone to grow the formations over time. Other minerals are brought into the cave by flowing of water to create white, red, tan, and gray colors on the formations and walls. St. Louis Limestone is primarily made of calcite, but is also known to contain magnesium sulfate, manganese dioxide, ferric oxide, gypsum, dolomite, and aragonite. On the show tour, deposits of calcite, manganese dioxide, and ferric
Calcium carbonate below sea level. Calcium carbonate can preserve fossils through permineralization. Most of the vertebrate fossils of the Two Medicine Formation—a geologic formation known for its duck-billed dinosaur eggs—are preserved by CaCO permineralization. This type of preservation conserves high levels of detail, even down to the microscopic level. However, it also leaves specimens vulnerable to weathering when exposed to the surface. Trilobite populations were once thought to have composed the majority of aquatic life during the Cambrian, due to the fact that their calcium carbonate-rich shells were more easily preserved than those of other species, which had purely chitinous shells. The