Solutional cave and most abundant solutional caves are located in limestone. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation. These include flowstones, stalactites, stalagmites, helictites, soda straws, calcite rafts and columns. These secondary mineral deposits in caves are called "speleothems". Limestone dissolves under the action of rainwater and groundwater charged with HCO (carbonic acid) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as "karst", characterized by sinkholes, and underground drainage. Solutional caves in this landform—topography are often called karst caves. Lechuguilla Cave in New Mexico and nearby Carlsbad Cavern are now believed
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