Moonmilk (sometimes called mondmilch, erroneously (influenced by "mountain") montmilch or rarely mundmilch) is a white, cheese-like substance found inside caves. It is similar to other deposits, but its unique quality is that it does not harden or turn to stone. It is a precipitate from limestone comprising aggregates of fine crystals of varying composition usually made of carbonate materials, e.g., calcite, hydromagnesite, and gypsum.
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