Minerals Found in Caves

Many interesting minerals are found in caves in addition to the calcite which forms the major features. Aragonite, a calcium carbonate mineral similar to calcite but not as common, often occurs in intricate needles known as anthodites. Gypsum (calcium sulfate) and related calcium sulfate minerals are next to calcite in abundance. Some caves, although they are developed in limestone, have extensive passages lined with fine, curling growths of gypsum flowers. In other caves, selenite (a less common variety of gypsum) forms long transparent rods or nests of fibrous crystals. Sulfates of sodium and magnesium are also found in caves, although they are less conspicuous than gypsum. Iron minerals in the form of oxides (limonite) and hydroxide (goethite) occur in caves and in some places form stalactites. Manganese minerals in caves are commonly present as thin, sooty coatings on walls and ceilings and in earth fills. Nitrocalcite (calcium nitrate) is abundant in earth fills in many caves, but individual fragments are generally microscopic. Barite (barium sulfate) and celestite (strontium sulfate) also occur in earth fills. In some solution caves, clay minerals exist in relatively pure forms; these include the less common varieties attapulgite and endellite.

In deep caves encountered during mining operations, a number of ore minerals have been found in the decorative wall draperies. Most common are azurite and malachite (forms of copper carbonate). About 50 other minerals also have been reported in cave deposits.