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).
Localities
At the Chah Mileh mine, Iran, a cerussite - mimetite - hemimorphite pseudomorph after descloizite has been found (KL p173).
At the Tsumeb mine, Oshikoto Region, Namibia, some specimens of mimetite and cerussite rank among the finest in the world. Both are secondary minerals formed from pre-existing lead minerals, the cerussite forming first, probably from the weathering of galena. Then the mimetite crystallised on the cerussite, after which the chemistry of the environment changed to dissolve away the cerussite, leaving an epimorph of mimetite; some specimens retain a solid cerussite core, others have only residual cerussite, while still others are devoid of cerussite altogether. Some specimens retain clear evidence of original twinning. Associated minerals, other than goethite and hematite, are relatively rare. One large pocket produced an abundance of distinctive specimens in which the cerussite was incompletely coated with powdery yellow mimetite and was associated with calcium-rich duftite (R&M 96.4.352-357 ). Other minerals that form pseudomorphs after cerussite include arsentsumebite, hydrocerussite and smithsonite (R&M 96.4.352-357 ). Also cerussite pseudomorphs after anglesite have been found (KL p172, 205).
At Berg Aukas, Grootfontein, Otjozondjupa Region, Namibia, cerussite occurs as a secondary mineral in the galena fraction of the ore bodies, associated with willemite, smithsonite and, rarely, quartz and goethite (R&M 96.2.123-124).
At the Barrow Mine, Above Derwent, Allerdale, Cumbria, England, UK, cerussite has been found on a galena and quartz matrix with abundant white to yellow coloured cerussite crystals and micro-acicular pyromorphite crystals (AESS).
At Force Crag Mine, Coledale, Above Derwent, Allerdale, Cumbria, England, UK, a small specimen of galena has been found with a dense coating of cerussite formed into ingrown crystals in a vug. In another specimen, an open face of matrix is covered with a combination of matte black sphalerite, white cerussite and typical brownish pyromorphite (AESS).
At Red Gill Mine, Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, a specimen was found with vugs containing a combination of cerussite, malachite and brochantite crystals with light blue chrysocolla. Another specimen featured cerussite associated with leadhillite (AESS).
At the Old Brandley Mine, Catbells, Keswick, Allerdale, Cumbria, England, UK, a specimen has been found with a micro-crystalline quartz matrix with a dense coverage of galena crystals showing advanced stages of alteration to cerussite crystals (AESS).
At the Clargillhead vein, Garrigill, Alston Moor, Eden, Cumbria, England, UK, cerussite is the most abundant supergene phase, commonly directly replacing galena but also as crystals infilling void spaces. The earliest cerussite occurs as replacement rims on galena. Close to the galena this cerussite is dark-coloured with minute inclusions of either galena or yarrowite. It is commonly overgrown by pale coloured, inclusion-free cerussite. This type of cerussite also forms euhedral, acicular to tabular crystals infilling void spaces. Locally, 60 to 200 micron diameter cerussite crystals carrying fine-grained copper sulphides are present in galena (JRS 23.51).
At the Whitwell quarry, Derbyshire, England, UK, cerussite occurs on a baryte-galena matrix (RES p137). Pyromorphite pseudomorphs after cerussite have been found here (KL p204).
At Croft quarry, Leicestershire, England, UK, cerussite has been found on galena crystals associated with analcime (JRS 20.13).
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 Roar Hill, Ballater, Buchan Grampian, Scotland, UK, lead-bearing vein mineralisation was exposed during recent work carried out on an unmetalled vehicle track. A small temporary quarry exposed fluorite-bearing quartz veins and minor wulfenite in light-coloured granite. At a second site, a little further to the west, an oxidised galena-bearing quartz vein was exposed.
Cerussite occurs as a white overgrowth on partly corroded galena crystals in vein quartz at the track exposure (JRS 22.32).
At the Potter-Cramer property, Maricopa County, Arizona, USA, cerussite occurs as colourless crystals that fluoresce bright yellow under LWUV. Associated minerals include wickenburgite, willemite and fluorite. The wickenburgite is usually colourless, and fluoresces pink to red (R&M 96.1.29).
At the Flux mine, Santa Cruz county, Arizona, USA, pseudomorphs of cerussite after anglesite have been found (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).
At the Kabwe mine, Central Province, Zambia, cerussite occurs almost invariably encrusted with hemimorphite, and sometimes with tarbuttite (R&M 94.2.123).
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 (MM 53.363-371).
duftite (s) and H2CO3 (aq) to cerussite (s), malachite (s), H2AsO4- (aq) and H+ (aq)
2PbCuAsO4(OH) + 3H2CO3 ⇌ 2PbCO3 + Cu2CO3(OH)2 + 2H2AsO4- + 2H+
(MM 52.688)
litharge + water + calcite = cerussite + Ca2+ + (OH)-
PbO + H2O + CaCO3 = PbCO3 + Ca2+ + 2OH-
(JRS 15.25-26)
Stability
The Activity-pH diagram below was calculated for some lead minerals. Boundaries are calculated for constant activity (roughly equivalent to concentration) of (SO4)2- and constant partial pressure (also roughly equivalent to concentration) of CO2, over a range of values of pH and of Cl1- activity. In this case the concentration of CO2 is appreciably more than the atmospheric value.
For seawater aCl- = 10-0.5 and pH = 8.2, so here cerussite is the stable mineral in contact with seawater.
Cerussite is stable in an alkaline or slightly acid environment and a wide range of Cl- ions. If the concentration of CO2 decreases the stability field of cerussite narrows to become more alkaline (higher pH) then disappears in favour of hydrocerussite (JRS 15.18-23).
The lead mineral formulae are:
cotunnite PbCl2
phosgenite Pb2(CO3)Cl2
cerussite Pb(CO3)
anglesite Pb(SO4)
The Activity-pH diagram below is similar, but in this case the concentration of CO2 is less than the atmospheric value.
Hydrocerussite and cerussite can co-exist at this level of CO2 concentration. At higher concentrations cerussite is the stable mineral, and at lower concentrations Hydrocerussite is the stable mineral (JRS 15.21).
The lead mineral formulae are:
cotunnite PbCl2
paralaurionite PbCl(OH)
mendipite Pb3O2Cl2
cerussite Pb(CO3)
hydrocerussite Pb3(CO3)2(OH)2
anglesite Pb(SO4)
leadhillite Pb4(CO3)2(OH)2
The diagram below is similar, but in this case the concentration of CO2 is less than the atmospheric value.
Hydrocerussite and cerussite can co-exist at this level of CO2 concentrations. At higher concentrations cerussite is the stable mineral, and at lower concentrations hydrocerussite is the stable mineral (JRS 15.21).
The lead mineral formulae are:
cotunnite PbCl2
paralaurionite PbCl(OH)
mendipite Pb3O2Cl2
cerussite Pb(CO3)
hydrocerussite Pb3(CO3)2(OH)2
anglesite Pb(SO4)
leadhillite Pb4(CO3)2(OH)2
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