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Formula: Pb2O(SO4)
Anhydrous sulphate
Crystal System: Monoclinic
Specific gravity: 6.92 measured, 7 calculated
Hardness: 2 to 2½
Streak: White
Colour: Grey to greenish white, pale yellow
Solubility: Soluble in KOH and in warm nitric acid
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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