 It is a trigonal mineral which is white when pure.Monohydrocalcite is not a common rock-forming mineral, but is 
frequently associated with other calcium and magnesium carbonate minerals, such as calcite, aragonite, lansfordite, and nesquehonite.Monohydrocalcite has been observed in air conditioning systems, and in moonmilk deposits in caves, both probably formed from spray of carbonate rich fluids.