manganese mineral

Formula: Ba(Mn4+6Mn3+2)O16
cryptomelane group
Specific gravity: 4.95
Hardness: 6
Streak: Black
Colour: Slivery grey to black

Metamorphic environments
Hydrothermal environments

Hollandite is a primary mineral in contact metamorphic manganese ores, and a secondary weathering product of earlier manganese-bearing minerals, associated with bixbyite, braunite piemontite and other manganese oxides (HOM).
At Ilfeld, Harz mountains, Germany, hollandite occurs rarely in fissures in massive manganite ores, or encrusting baryte (Minrec 41.6.493).
At Kajlidongri, Jhabua state, India, hollandite occurs in quartz veins traversing a manganese orebody (Dana).
At Nuba Mountain, Kordofan Province, Sudan, hollandite occurs intergrown with pyrolusite (Dana).

Common impurities: Fe,Pb,K,Na

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