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Limestone rocks are those which contain more than 50% calcite (calcium carbonate) mineral. Extensive karst forms in limestone areas as the minerals react chemically with dissolved carbon dioxide and organic acids. Although limestone is slightly soluble in water, the reaction with carbonic acid appears to be the primary solution reaction. Although calcite is usually the most abundant mineral, other common minerals include aragonite, dolomite, and magnesite (magnesium carbonate). Impurities, which tend to inhibit or slow down karstification, include chert, flint, authigenic (formed in place) quartz and feldspar, and clay minerals. Limestone is considered a carbonate rock.
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