Caledonite

sulphate

cerussite

Formula: Cu2Pb5(SO4)3(CO3)(OH)6
Compound sulphate
Specific gravity: 5.75 to 5.77
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

Hydrothermal environments

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).

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 Driggith Mine, Caldbeck, Allerdale, Cumbria, UK, caledonite occurs with leadhillite and linarite, or with linarite in oxidation rims surrounding galena (JRS 9.16).

At Balliway Rigg, Roughton Gill, Caldbeck, Allerdale, Cumbria, UK, caledonite occurs in a quartz-galena matrix associated with leadhillite and its polymorph susannite, and the rare mineral mattheddleite; it also occurs in cavities in vein quartz with linarite, leadhillite and susannite (JRS 11.9-10).

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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