birnessite
Sign in to saveBirnessite (nominally MnO2·nH2O), also known as δ-, is a hydrous manganese dioxide mineral with a chemical formula of Na0.7Ca0.3Mn7O14·2.8H2O. It is the main manganese mineral species at the Earth's surface, and commonly occurs as fine-grained, poorly crystallized aggregates in soils, sediments, grain and rock coatings (e.g., desert varnish), and marine ferromanganese nodules and crusts. It was discovered at Birness, Aberdeenshire, Scotland.
Key facts
- Mineral.name
- Birnessite
- Mineral.category
- Oxide mineral
- Mineral.image
- birnessite 01.jpg
- Mineral.imagesize
- 260px
- Mineral.formula
- MnO2·nH2Oδ-
- Mineral.IMAsymbol
- Bir
- Mineral.system
- Triclinic or Hexagonal
- Mineral.color
- Dark brown to black
- Mineral.habit
- Extremely finely crystalline
- Mineral.cleavage
- [001] perfect
- Mineral.mohs
- 1.5
- Mineral.luster
- Sub-metallic, dull
- Mineral.refractive
- nω = 1.730 nε = 1.690
- Mineral.opticalprop
- Uniaxial (−)
- Mineral.birefringence
- δ = 0.040
- Mineral.gravity
- 3.0
- Mineral.diaphaneity
- Nearly opaque
- Mineral.other
- Identification by optical properties is impossible.
via Wikipedia infobox
Wikidata facts
- Image
- Birnessite 01.jpg
Show 7 more facts
- IMA Mineral Symbol
- Bir
- Nickel-Strunz 9th edition (updated 2009)
- 4.FL.45
- density
- 1.5
- Nickel-Strunz '10th ed', review of (9th ed/ 2009 update)
- 4.FL.45
- Commons category
- Birnessite
- chemical formula
- (Na,Ca,K)₀.₆(Mn⁴⁺,Mn³⁺)₂O₄·(H₂O)₁.₅
- Strunz 8th edition (series ID, updated)
- IV/D.03e
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~7 min read
Article
6 sectionsContents
- Formation
- Composition and structure
- Surface reactivity
- Properties and applications
- See also
- References
Birnessite (nominally MnO2·nH2O), also known as δ-, is a hydrous manganese dioxide mineral with a chemical formula of Na0.7Ca0.3Mn7O14·2.8H2O. It is the main manganese mineral species at the Earth's surface, and commonly occurs as fine-grained, poorly crystallized aggregates in soils, sediments, grain and rock coatings (e.g., desert varnish), and marine ferromanganese nodules and crusts. It was discovered at Birness, Aberdeenshire, Scotland.
== Formation == Its precipitation from the oxidation of Mn(II) in oxygenated aqueous solutions is kinetically hindered and slow on mineral surfaces. Biological Mn(II) oxidation is generally fast relative to abiotic Mn(II) oxidation processes, and for this reason the majority of natural birnessites is believed to be produced by microorganisms, especially bacteria, but also fungi.
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