Parkinsonite

parkinsonite

chloroxiphite

diaboleite

mendipite

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Formula: Pb7MoO9Cl2
Oxyhalide, molybdenum-bearing mineral
Specific gravity: 7.32
Hardness: 2 to 2½
Streak: Dark red
Colour: Red to purplish-red
Environments

Hydrothermal environments

Parkinsonite occurs in fractures and vugs in carbonates associated with iron and manganese oxides (Webmin).

Localities

The Kombat Mine, Kombat, Grootfontein, Otjozondjupa Region, Namibia. Parkinsonite has been found to occur in specimens labelled as being from Tsumeb, although it is suspected that these actually may be from the Kombat Mine. The chemical conditions at Tsumeb do not seem to allow for the formation of oxychlorides, which require very specific conditions, but the appropriate conditions did exist at the Kombat mine. Also it was common practice in Namibia to label specimens from Kombat and other localities as being from Tsumeb, in order to enhance their price. Interestingly, parkinsonite on a ‘Tsumeb’ specimen recently studied at the Natural History Museum, London, occurs with a fibrous lead-manganese oxychloride believed possibly to be rickturnerite, but it is suggested that the Kombat Mine is the true locality, as an extremely high pH (alkaline environment) is required to form rickturnerite(JRS 13.28).

There are two co-type localities, Wesley mine, Westbury on Trym, Bristol, and Torr Works Quarry (Merehead Quarry), Cranmore, Mendip, Somerset, both in England, UK.

At the Torr Works Quarry (Merehead Quarry), Cranmore, Mendip, Somerset, England, UK, parkinsonite is a very rare mineral in nodules in manganese oxide ores in veins, fissures, and pockets in limestone. Associated minerals include mendipite, chloroxiphite, diaboleite, cerussite, paralaurionite, wulfenite, calcite and manganese oxides (HOM).
During the 1960s the Natural History Museum, London, acquired minerals typical of the exposures in Merehead Quarry. Many of the specimens contain fine groups of mendipite enclosing chloroxiphite within a matrix of cerussite, calcite and unidentified manganese oxides. Some mendipite specimens have their cleavage marked by small bright red crystalline patches of parkinsonite. Specimens collected in situ, associated with cerussite and mendipite, were from a manganese-rich pod in the limestone formation. In this association, parkinsonite occurs as small patches of cleavage plates and crystalline aggregates in cerussite, hydrocerussite and mendipite. Less commonly, parkinsonite is associated with wulfenite or with a boron-bearing lead oxychloride mineral (MM 58.59-68).

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