Hollandite | |
---|---|
General | |
Category | Oxide minerals |
Formula (repeating unit) | Ba(Mn4+6Mn3+2)O16 |
IMA symbol | Hol [1] |
Strunz classification | 4.DK.05a |
Dana classification | 7.9.1.1 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) |
Space group | Monoclinic H-M symbol: (2/m) Space group: I2/m |
Identification | |
Color | Silvery-grey to greyish |
Cleavage | Distinct / Good, Prismatic |
Mohs scale hardness | 4 to 6 |
Density | 4.95 [2] |
Hollandite (chemical formula: Ba(Mn4+6Mn3+2)O16) is a manganese oxide mineral. [2] Its structure consists of double chains of MnO6 octahedra delimiting 2 × 2 tunnels. The electrostatic charge created by the Mn3+ for Mn4+ substitution is balanced by cations in the tunnels. Their nature determines the mineral species: Ba for hollandite, K for cryptomelane, Pb for coronadite, Sr for strontiomelane, [3] Tl for thalliomelane, [4] and Na for manjiroite. [5] Pure species are rare and most 2 × 2 tectomanganates contain mixtures of several types of tunnel cations.
A mineral, with the chemical composition BaMn4+6Fe3+2O16, [6] that was first found in the Kajlidongri mine in the Jhabua district of Madhya Pradesh, India, [7] had the name hollandite until it was reclassified as ferrihollandite by the International Mineralogical Association in 2012. Ferrihollandite is the barium-iron (III) endmember of the coronadite group. [2]
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