Hereroite

hereroite

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Formula: [Pb32(O,◻)21](AsO4)2[(Si,As,V,Mo)O4]2Cl10
Lead oxychloride ( oxychorides have both oxygen and chlorine atoms attached to lead atoms in a single molecule; other components may also be present), arsenic-, vanadium- and molybdenum- bearing mineral
Crystal System: Monoclinic
Specific gravity: 8.15 calculated for the empirical formula
Streak: White
Colour: Bright orange
Environments

Metamorphic environments
Hydrothermal environments

Hereroite is a relatively new mineral, approved in 2011 and to date (March 2025) reported only from the type locality.

Localities

At the type locality, the Kombat Mine, Kombat, Otavi Constituency, Otjozondjupa Region, Namibia, the orebodies contain primary lead - copper - zinc - silver sulphides that were originally emplaced hydrothermally as fracture fillings; they were subsequently modified by hydrothermal and metasomatic replacement events, including a phase of iron - manganese silicification. These events created a range of lead - manganese - iron silicate minerals in the deposit, and a variety of late-stage lead-oxyhalide minerals including hereroite and vladkrivovichevite.
Work in the Mendip Hills, where similar minerals are found, indicates that the oxychlorides are formed at the end of the paragenetic process, at low temperatures and over a wide range of pH (acidity) conditions. Similar conditions probably prevailed at the Kombat mine when hereroite and vladkrivovichevite crystallised.
Hereroite is relatively abundant on the type specimen as transparent to translucent intergrown glassy orange grains. The individual grains are generally less than 1 mm in size and they form aggregates up to ~3 mm. On one corner of the specimen hereroite forms relatively well defined crystals to ~0.5 mm. Hereroite and vladkrivovichevite are associated with other oxyhalide minerals including asisite, damaraite, kombatite and sahlinite. On the type specimen, asisite is most abundant as glassy greenish yellow crystalline masses up to 3 mm across. Kombatite also occurs as orange-brown aggregates of grains (<1 mm across) which are visually very similar to hereroite. The matrix of the specimen is made up of clear to white granular vein quartz containing irregular grains of oxychloride minerals, barysilite, abundant manganese silicates, rare native copper and minute grains, less than 0.2 mm, of manganese oxyhydroxide minerals. These have not been identified due to their small size, but other oxychloride specimens from the Kombat mine typically contain a mixture of hausmannite, jacobsite and manganite (MM 76.4.883-890).
Hereroite from the Kombat Mine - Image

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