Lanarkite

sulphate

galena

Formula: Pb2O(SO4)
Anhydrous sulphate
Specific gravity: 6.92
Hardness: 2 to 2½
Streak: White
Colour: Grey to greenish white, pale yellow
Solubility: Soluble in KOH and in warm nitric acid
Environments:

Hydrothermal environments

Lanarkite is a rare secondary supergene mineral in the oxidised zone of galena deposits, associated with cerussite, leadhillite, susannite, hydrocerussite and caledonite (HOM).
At extremely low carbonate concentrations lanarkite can form in conditions of pH between those for anglesite and leadhillite. A carbonate concentration this low requires the presence of a relatively strong alkali, much stronger than could be developed from the dissolution of calcite at atmospheric levels (JRS 18.11). Otherwise lanarkite requires an unusually high pH (very alkaline environment) for its formation (JRS11.45).
Lanarkite alters to cerussite, leadhillite and anglesite (Mindat).

At Balliway Rigg, Caldbeck Fells, Cumbria, England, UK, a small number of lanarkite specimens were found in an oxidised galena vein. Some crystals are completely replaced by leadhillite, and leadhillite epimorphs after lanarkite are present on a number of specimens. Drusy mattheddleite commonly overgrows lanarkite and it is occasionally associated with caledonite. Although many of the specimens are associated with partly oxidised galena, galena is not present in every case (JRS11.15).

At the Driggith mine, Caldbeck Fells, Cumbria, England, UK, lanarkite has been found on two specimens in cavities in corroded galena. On one specimen lanarkite is associated with leadhillite, anglesite and chenite and in the second with anglesite (JRS 9.39-44).

At Silver Gill, Caldbeck Fells, Cumbria, England, UK, lanarkite was identified on a single specimen as minute crystals in a quartz cavity containing remnant galena (JRS8(2).85-97).

At the type locality, the Susanna mine, Leadhills, Scotland, UK, lanarkite is associated with leadhillite, cerussite and caledonite (Dana, Mindat).

At the the Gallagher Vanadium Property and Manila Mine, Cochise County, Arizona, USA, lanarkite has been found in one occurrence as small crystals on leadhillite and anglesite in the altered crust of a galena nodule (R&M 90.4.344).

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