Birnessite
A variety of Minerals
What is Birnessite?
Birnessite (Na0.3Ca0.1K0.1)(Mn,Mn)2O4 · 1.5 H2O is an oxide mineral 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 Mohs 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.
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Birnessite Localities Map
See where Birnessite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
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North ZoneCentral RidgeSouth Basin
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© Alain Manceau
Quick Facts
Physical Properties
- Color
- Black; dark brown in transmitted light
- Hardness (Mohs)
- 1.5
- Density
- 3.4 g/cm³
- Streak
- Dark brown to brown
Chemical Properties
- Chemical Formula
- (Na,Ca)0.5(Mn4+,Mn3+)2O4 · 1.5H2O
- Elements
- Ca, H, Mn, Na, O
Also Known As
BirnessiteManganese OxidesΔ-mno2
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