Mineralpedia Details for Hydromagnesite
Named for the water content and its similarity to magnesite. Widespread with many minor localites, but still uncommon, Hydromagnesite is well studied from localities in the united Staes, Canada, Brazil, Italy, Austria, France, Iran, Zimbabwe, and Antarctica. Hydromagnesite is the most common carbonate in caves after calcite and aragonite. In caves it is a common component of speleothems and “moonmilk,” which is a white, creamy substance found in caves that never hardens. It also forms in hydrothermally altered dolomite xenoliths, marble, and altered ultramafic rocks and serpentinites as incrustations and a fracture filling.
Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/hydromagnesite.pdf
Hydromagnesite from Lee River Valley, near Nelson, South Island, New Zealand
Radial, flat, white crystals 5mm.
Hydromagnesite from Aurora mine, San Benito Co., California, United States
Snow white incrustation of Hydromagnesite as "bubbly" growths on matrix.
Hydromagnesite from Eibenthal, Almas Mts, Mehedinti Co., Romania
Snow white sprays to 1mm. Ex. Paul Nicholson collection with tag (see prov. tab).