In it are formations such as helctites (eccentric stalactites defying gravity) and curtains (draperies, or sheets of calcite, sometimes translucent, hanging from the ceiling).
en.wikipedia.org Rivers which emerge from springs may produce tufa terraces, consisting of layers of calcite deposited over extended periods of time.
en.wikipedia.org The mineral occurs in cavities in sedimentary iron and manganese deposits in association with arsenoclasite, shigaite, hematite, hausmannite, triploidite, barite, and manganoan ferroan calcite.
en.wikipedia.org Associated minerals include azurite, calcite, malachite, and smithsonite.
en.wikipedia.org A second great group of hornfels are the calcite-silicate hornfels that arise from the thermal alteration of impure limestone.
en.wikipedia.org