Hollandite

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 x 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 x 2 tectomanganates contain mixtures of several types of tunnel cations.

Hollandite
General
CategoryOxide minerals
Formula
(repeating unit)		Ba(Mn4+6Mn3+2)O16
IMA symbolHol[1]
Strunz classification4.DK.05a
Dana classification7.9.1.1
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
Space groupMonoclinic
H-M symbol: (2/m)
Space group: I2/m
Identification
ColorSilvery-grey to greyish
CleavageDistinct / Good, Prismatic
Mohs scale hardness4 to 6
Density4.95[2]

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]

  • Hollandite star in rare quartz inclusion
    Hollandite star in rare quartz inclusion
  • Polyhedral representation of the 2 x 2 tunnel structure of hollandite. The black atoms represent Ba.
    Polyhedral representation of the 2 x 2 tunnel structure of hollandite. The black atoms represent Ba.[8]

See also

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. "Hollandite". Mindat.org. Retrieved 15 February 2022.
  3. Mindat.org
  4. Mindat.org
  5. Mindat.org
  6. "Archived copy". Archived from the original on 2017-04-02. Retrieved 2017-04-01.{{cite web}}: CS1 maint: archived copy as title (link)
  7. "Hollandite" (PDF). Rruff.info. p. 252. Retrieved 15 February 2022.
  8. Post JE, Von Dreele RB, Buseck P (1982) Acta Crystallographica B38: 1056-1065
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