Moonmilk (sometimes called mondmilch, also known as montmilch or as cave milk) is a white, creamy substance found inside limestone, dolomite, and possibly other types of caves. It is a precipitate from limestone comprising aggregates of fine crystals of varying composition usually made of carbonates such as calcite, aragonite, hydromagnesite, and/or monohydrocalcite. Being soft, moonmilk was frequently the medium for finger fluting, a form of prehistoric art. The world's largest formation of brushite moonmilk is found in the Big Room of Kartchner Caverns State Park in southern Arizona.