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.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Birnessite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
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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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
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Birnessite FAQs
How do I identify Birnessite?
Birnessite can be identified by its hardness of 1.5 on the Mohs scale, Black; dark brown in transmitted light color. Look for these key characteristics when examining specimens.
What color is Birnessite?
Birnessite typically appears in Black; dark brown in transmitted light. Color can vary depending on impurities and formation conditions.
How hard is Birnessite?
Birnessite has a hardness of 1.5 on the Mohs scale. This makes it a soft mineral that can be scratched easily.
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