Birnessite
Manganese hydroxide mineral / From Wikipedia, the free encyclopedia
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Birnessite (nominally MnO2·nH2O), also known as δ-MnO2, is a hydrous manganese dioxide mineral with a chemical formula of Na0.7Ca0.3Mn7O14·2.8H2O.[5] 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.[6][7][8][9][10][11][12] It was discovered at Birness, Aberdeenshire, Scotland.
Quick Facts General, Category ...
Birnessite | |
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General | |
Category | Oxide mineral |
Formula (repeating unit) | MnO2·nH2O δ-MnO2 |
IMA symbol | Bir[1] |
Crystal system | Triclinic or Hexagonal |
Identification | |
Color | Dark brown to black |
Crystal habit | Extremely finely crystalline |
Cleavage | [001] perfect |
Mohs scale hardness | 1.5 |
Luster | Sub-metallic, dull |
Diaphaneity | Nearly opaque |
Specific gravity | 3.0 |
Optical properties | Uniaxial (−) |
Refractive index | nω = 1.730 nε = 1.690 |
Birefringence | δ = 0.040 |
Other characteristics | Identification by optical properties is impossible. |
References | [2][3][4] |
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