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
Carbonate-hosted lead-zinc ore deposits within the supergene zone. MVT and Irish type deposits are commonly associated with a 'dolomite front' alteration, which manifests as a yellow-cream wash of dolomite (calcium-magnesium carbonate) within calcite-aragonite assemblages of unaltered carbonate formations. Most ore bodies are quite sulfidic, and most are very low-iron, with pyrite-marcasite contents typically below 30% of the mass of sulfides. This makes MVT lead-zinc deposits particularly easy to treat from a metallurgical view. Some MVT deposits can, however, be very iron-rich and some sulfide replacement and alteration zones are associated with no lead-zinc at all, resulting in massive accumulations of pyrite-marcasite, which are essentially