Cerussite

cerussite

lead

Formula: Pb(CO3)
Carbonate, lead mineral
Specific gravity: 6.4 - 6.6
Hardness: 3 to 3½
Streak: White
Colour: Colourless, white, grey, yellow, brown, blackish (from inclusions of galena)
Solubility: Slightly soluble in hydrochloric acid and sulphuric acid; moderately soluble in nitric acid
Environments:

Carbonatites
Hydrothermal environments

Cerussite is generally a secondary mineral that occurs in the oxidation zone of high temperature lead-zinc deposits. It also occurs as alteration pseudomorphs after anglesite, phosgenite, leadhillite, caledonite, hydrocerussite, bournonite, linarite, pyromorphite and vanadinite. and also as substitution pseudomorphs after calcite and sphalerite.

Lead will generally precipitate as primary galena from ore fluids rich in sulphur and lead. Removal of sulphur by precipitation of sulphides, however, may lead ultimately to an ore fluid from which galena cannot be precipitated, even with a high concentration of lead in solution. In these circumstances, cerussite, as well as pyromorphite and anglesite, could be precipitated as a primary mineral (Strens (1963), MM 33:722-3).

Anglesite and cerussite do not usually occur together. Generally anglesite is stable in lower pH (more acid) environments and cerussite in higher pH (more alkaline) environments. Seawater has a pH of approximately 8.3 (somewhat alkaline) so cerussite is the stable lead supergene mineral in contact with seawater (JRS 18.9,11).
For carbonate concentration slightly lower than atmospheric, cerussite and hydrocerussite can co-exist in alkaline environments, with leadhillite in more acid environments, and anglesite in yet more acid environments. For lower carbonate concentrations hydrocerussite completely replaces cerussite (JRS 18.11).

At the Whitwell quarry, Derbyshire, England, UK, cerussite occurs on a baryte - galena matrix (RES p137).

At the Snailbeach mine, near Minsterley, Shropshire, England, UK, cerussite occurs on quartz (RES p276).

At the Judkins quarry, Nuneaton, Warwickshire, England, UK, cerussite occurs with galena and calcite (RES p323).

At the Flux mine, Santa Cruz county, Arizona, USA, pseudomorphs of cerussite after anglesite have been found (R&M 94.2.123).

At the Kabwe mine, Central Province, Zambia, cerussite occurs almost invariably encrusted with hemimorphite, and sometimes with tarbuttite (R&M 94.2.123).

At Cookes Peak mining district, Luna county, New Mexico, USA, cerussite was the dominant ore, produced as an oxidation product of galena (R&M 94.3.226).

Alteration

In the oxidation zone of epithermal veins primary galena PbS alters to secondary cerussite PbCO3 or anglesite depending on the acidity. Cerussite forms in more basic (alkaline) environments than anglesite (AM 100:1584-1594).

Formation of cerussite
galena may dissolve in carbonic acid from percolating rainwater to form lead ions, Pb2+.
PbS + 2H2CO3 → Pb2+ + H2S + 2HCO3>-
(KB).
These lead ions may then combine with carbonate ions CO32- to form cerussite, which is virtually insoluble in water and weak acids.
Pb2+ + CO32- → PbCO3

cerussite and aqueous H2AsO4-, Cl- and H+ to mimetite and aqueous H2CO3
5PbCO3 + 3H2AsO4- + Cl- + 7H+ ⇌ Pb5(AsO4)3Cl + 5H2CO3
or
5PbCO3 + 3HAsO42- + Cl- + 4H+ ⇌ Pb5(AsO4)3Cl + 5H2CO3
cerussite and mimetite can co-exist only under basic conditions at rather high PCO2 (Min Mag June 1989 Vol 53 pps363-371).

litharge + water + calcite = cerussite + Ca2+ + (OH)-
PbO + H2O + CaCO3 = PbCO3 + Ca2+ + 2OH-
(JRS 15.25-26)

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