Hollandite - Encyclopedia

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

Hollandite from Yavapai County, Arizona, USA © Danny Jones

Hollandite from Praborna Mine, Saint-Marcel, Aosta Valley, Italy © Enrico Bonacina

Hollandite in quartz from Anketsaketsa, Madagascar © Michael C. Roarke

11.95 ct citrine with hollandite inclusions from Brazil

Hollandite in the World

The best known crystals, centimeter prisms, come from Indian deposits (Kajlidongri and Sitapur), but hollandite is quite common in German, American and Moroccan manganese deposits. Magnificent acicular inclusions are known in quartz from Anketsaketsa (Madagascar).

Hollandite in France

In France, hollandite is present at the Haut-Poirot mine (Vosges), it is also known at Echassières (Allier), Peyrebrune (Tarn) and Roumazières (Charente).

Twinning

Twins are known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 4 to 6
Density : 4.95
Fracture : Undeterminated
Streak : Black

TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None

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