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Formula: Cu2Pb5(SO4)3(CO3)(OH)6
Compound sulphate
Crystal System: Orthorhombic
Specific gravity: 5.75 to 5.77 measured, 5.689 calculated
Hardness: 2½ to 3
Streak: Greenish-blue to bluish-white, paler than the sample
Colour: Dark blue to bluish-green; light bluish green in transmitted light
Solubility: Soluble in nitric acid with effervescence
Caledonite is an uncommon secondary
mineral in the oxidised portions of lead-copper deposits. Alteration to
cerussite has been observed.
Linarite and caledonite are both important lead/copper supergene minerals; both
minerals can be found alone in cavities although they can also occur together, and both are often associated with simple lead
and copper minerals such as cerussite and
brochantite and, to a lesser extent,
malachite; they can be found in such combinations in the
carbonate rich English Pennines.
Caledonite occurs in environments where the pH lies between that of anglesite
(more acid) and linarite/cerussite
(more alkaline)
(JRS 18.14).
Localities
At Pilbara, Western Australia, caledonite occurs associated with linarite,
cerussite, brochantite and
malachite. It sometimes forms a massive coating on
cerussite
(AJM 13.2.58).
At Balliway Rigg, Caldbeck, Allerdale, Cumbria, UK, caledonite occurs in a
quartz-galena
matrix associated with leadhillite and its
paramorph
susannite, and the rare
mineral mattheddleite; it also occurs
in cavities in vein quartz with
linarite, leadhillite and
susannite
(JRS 11.9-10).
At Driggith Mine, Caldbeck, Allerdale, Cumbria, UK, caledonite occurs with
leadhillite and
linarite, or with linarite in oxidation
rims surrounding galena
(JRS 9.16).
At Brae Fell Mine, Roughton Gill, Caldbeck, Allerdale, Cumbria, UK, caledonite occurs associated with
linarite, or with
leadhillite and cerussite
(JRS 9.40).
At Red Gill Mine, Roughton Gill, Caldbeck, Allerdale, Cumbria, UK, caledonite occurs in cavities in
quartz associated with
leadhillite, linarite,
cerussite, anglesite and
mattheddleite, which is very rare worldwide, but
not uncommon here
(JRS 11.34-35).
In the Otto Mountains, Baker, California, USA, caledonite is sometimes associated with
linarite
(R&M 86.2.140).
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