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Birnessite (Na0.3Ca0.1K0.1Mn4+Mn3+O4·1.5(H2O)) is an mineral oxide of manganese along with calcium, potassium and sodium. It has a dark brown to black color with a submetallic luster. It is also very soft, with a hardness of 1.5. Birnessite is formed by precipitation in lakes, oceans and groundwater and is a major component of desert varnish and deep sea manganese nodules.

It was first described in 1956 and named for an occurrence in Birness, Aberdeenshire, Scotland.


  • Mindat with location data
  • Webmineral data
  • Mineral Data Publishing - PDF
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Birnessite". A list of authors is available in Wikipedia.
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