Class : Oxides and hydroxides
    Subclass : Oxides
    Crystal system : Monoclinic
    Chemistry : BaMn₈O₁₆
    Rarity : Quite common

Hollandite is a mixed oxide of manganese and barium. Its composition is changeable, barium can be partially replaced by lead, potassium or sodium, manganese by iron. It forms in manganese deposits, under the action of light metamorphism, or hydrothermal fluids which remobilize the manganese : in the latter case, hollandite crystallizes in quartz stringers cutting the massive oxides. It was named in honor of Thomas Henry Holland, Director of the Geological Survey of India and President of the University of Edinburgh. Hollandite forms chunky, centimeter-sized prismatic crystals but more commonly compact, fibrous or earthy masses that are sometimes concretionary. Hollandite has a shiny to dull metallic luster, black to grayish black or silver gray color. It is a manganese ore and can, when included in certain quartz, reach the fields of jewelry.

Main photo : Hollandite from Clara Mine, Germany © Volker Heck

Twins are known for this mineral species.

No fakes recorded for this mineral species.