Hydrocerussite
Hydrocerussite is basic lead carbonate, Pb3(CO3)2(OH)2: hexagonal, one perfect {0001} cleavage, hardness 3.5, density 6.80–6.82. Its cell, its kin, its places.
Hydrocerussite is basic lead carbonate, Pb3(CO3)2(OH)2, on both the September 2026 IMA list and its Handbook sheet: hexagonal, colourless to white, adamantine and pearly on its one perfect {0001} cleavage, hardness 3.5, density 6.80–6.82. Worked from standard atomic weights it is 80.14% lead. The sheet calls it an uncommon secondary mineral of oxidised lead deposits.
In short
- The species. The Handbook of Mineralogy sheet gives steep hexagonal pyramidal to tabular crystals to 4 cm, lenticular to thin scaly aggregates and cleavable masses; a perfect {0001} cleavage, irregular fracture, brittle; hardness 3.5; density 6.80–6.82. It is uniaxial (−), ω = 2.09 and ε = 1.94. The September 2026 IMA-CNMNC Master List row reads Pb3(CO3)2(OH)2, status G, 1877, Sweden.
- The cell check. A hexagonal cell holds (√3/2)·a²·c: with a = 5.239 Å and c = 23.65 Å that is 562.16 ų. Three formula units of 775.63 g/mol in it give a density of 6.873, the figure the sheet prints as calculated. The measured 6.80–6.82 sits 0.8–1.1% below it.
- The basic-carbonate ladder. By script, 3 IMA rows are built from lead, carbon, oxygen and hydrogen alone: hydrocerussite at 0.667 carbon per lead, somersetite at 0.625 and plumbonacrite at 0.600. Cerussite, with no hydrogen, has 1. Lead by mass climbs the other way: 77.54%, 80.14%, 81.19%, 81.83%.
- Documented failure: the old label. The plumbonacrite sheet cites Dana’s 1951 hydrocerussite entry as “[hydrocerussite, part]”, and somersetite, described in 2018 from Torr Works (‘Merehead quarry’), Somerset, is hexagonal, white, adamantine, with a perfect {0001} cleavage. A Mendip “hydrocerussite” label written before 2018 cannot have been checked against somersetite.
- Where it is found. The sheet’s Distribution includes Långban, Sweden; the Mendip Hills (Higher Pitts Farm, and large crystals at the Merehead quarry); Caldbeck Fells; Leadhills and Wanlockhead; the Kamariza mine, Laurium; Tsumeb; and exceptional crystals from the Mammoth-St. Anthony mine, Tiger, Arizona.
| Species | IMA formula; status, year | System | Cleavage (sheet) | Hardness | Density (sheet) | C per Pb | OH per Pb | Pb by mass | 20.00 g in water |
|---|---|---|---|---|---|---|---|---|---|
| Cerussite | Pb(CO3); G, 1845 | Orthorhombic | {110} and {021} good | 3–3.5 | 6.55 meas. | 1.000 | 0 | 77.54% | 16.95 g |
| Hydrocerussite | Pb3(CO3)2(OH)2; G, 1877 | Hexagonal | {0001} perfect | 3.5 | 6.80–6.82 meas. | 0.667 | 0.667 | 80.14% | 17.06–17.07 g |
| Somersetite | Pb8O(OH)4(CO3)5; A, 2017-024 | Hexagonal | {0001} perfect | ~3 | 7.01 calc.; meas. n.d. | 0.625 | 0.500 | 81.19% | 17.15 g (calc.) |
| Plumbonacrite | Pb5(CO3)3O(OH)2; Rd, 1889 | Hexagonal | None printed | n.d. | 7.07 (synthetic) | 0.600 | 0.400 | 81.83% | 17.17 g |
What is hydrocerussite? Basic lead carbonate with one perfect cleavage
Hydrocerussite is Pb3(CO3)2(OH)2, a hexagonal lead carbonate that carries hydroxyl. The Handbook of Mineralogy hydrocerussite sheet describes steep hexagonal pyramidal to tabular crystals to 4 cm, lenticular to thin scaly crystal aggregates and cleavable masses. Cleavage is perfect on {0001}, fracture irregular, tenacity brittle, hardness 3.5, density 6.80–6.82 measured. It is transparent to translucent, colourless to white or gray, and may show a greenish tint; the lustre is adamantine, pearly on {0001}. The optical class is uniaxial (−), ω = 2.09 and ε = 1.94; the ε figure was read from the rendered sheet because the text extraction drops the symbol.
The formula, worked. The September 2026 IMA-CNMNC Master List row reads hydrocerussite, Pb3(CO3)2(OH)2, status G (grandfathered), 1877, Sweden, the same formula the sheet heads. On standard atomic weights the molar mass is 775.63 g/mol and lead is 80.14% of it. Expressed as oxides that is PbO 86.33%, CO2 11.35% and H2O 2.32%, the three figures of the sheet’s ideal column.
The name. The sheet says it is named in allusion to its essential components, water and the lead and carbonate of cerussite. It gives type material as n.d. and marks no type locality, so this page names none; the term is explained at what a type locality is. It calls hydrocerussite an uncommon secondary mineral in the oxidized portions of lead deposits.
Does the hydrocerussite formula match its cell? The cell check and the Mendip analysis
The printed cell reproduces the printed calculated density exactly: 6.873. A hexagonal cell has a volume of (√3/2)·a²·c. With the sheet’s a = 5.239 Å and c = 23.65 Å that is 562.16 ų, and three formula units of 775.63 g/mol in it give 3 × 775.63 ÷ (0.60221 × 562.16) = 6.873 g/cm³. The sheet’s measured density, 6.80–6.82, is 0.989 to 0.992 of that figure. The space group is printed as n.d., so this page says nothing about the structure beyond the cell.
The Mendip analysis, worked. The sheet’s analysis (1), from the Mendip Hills, England, prints CO2 11.21, PbO 86.52, Cl 0.27 and H2O 2.23. Converted to moles and scaled to three lead atoms, that is 1.97 carbon and 1.92 hydroxyl against the ideal 2 and 2, with 0.06 chlorine. The analysis carries 80.32% lead, against 80.14% for the ideal formula.
What the sheet does not print. It gives an X-ray powder pattern, on synthetic material and “near to plumbonacrite”, with its strongest line at 2.623 Å; it prints no streak, no luminescence and no Raman data. A ligature-aware search of its text for fluorescence finds nothing, while the same search matches the hemimorphite and willemite sheets, its positive controls. That is silence, not a test result; is cerussite fluorescent covers the lead carbonates that do print a glow.
Hydrocerussite, plumbonacrite or somersetite? The basic-carbonate ladder
Three IMA rows are made of lead, carbon, oxygen and hydrogen alone, and hydrocerussite has the most carbon per lead of them, 0.667. A script over the September 2026 IMA list for formulas whose element set is exactly Pb, C, O and H, cross-checked by a raw line scan, finds hydrocerussite, Pb3(CO3)2(OH)2 (G, 1877); somersetite, Pb8O(OH)4(CO3)5 (A, 2017-024, United Kingdom), at 0.625; and plumbonacrite, Pb5(CO3)3O(OH)2 (Rd, 1889, United Kingdom), at 0.600. Cerussite, Pb(CO3), has no hydrogen and sits at 1.000. Lead by mass runs the other way: cerussite 77.54%, hydrocerussite 80.14%, somersetite 81.19%, plumbonacrite 81.83%.
Documented failure: a Mendip or Wanlockhead “hydrocerussite” label may not be hydrocerussite. The plumbonacrite sheet’s first reference is Dana’s System, 7th edition, 1951, volume II, page 270, marked “[hydrocerussite, part]”, and its Distribution is Wanlockhead and the Mammoth-St. Anthony mine, both also on the hydrocerussite sheet. The somersetite sheet cites its 2018 description as “a new complex hydrocerussite-related mineral from the Mendip Hills”, and gives a single locality: Torr Works quarry (‘Merehead quarry’), near Cranmore, Somerset, the quarry the hydrocerussite sheet names for large crystals. Somersetite is hexagonal, white or green, adamantine and brittle, with a perfect {0001} cleavage: the same field marks.
What the sheets separate them on. Somersetite is biaxial (−) with a calculated refractive index of 2.00, against hydrocerussite’s uniaxial (−); its hardness is about 3 and its calculated density 7.01, against 3.5 and 6.80–6.82. Plumbonacrite is recorded only as scaly crystals to 0.1 mm, pearly, with a synthetic density of 7.07. In water a 20.00 g piece would read 17.06–17.07 g as hydrocerussite and 17.15 g or 17.17 g as the other two: gaps of 0.08 to 0.11 g, too small to name a specimen. Optics and analysis decide; the method behind the balance figures is how to measure specific gravity at home.
Where is hydrocerussite found? Mendip, Leadhills, Laurium and Tiger
The hydrocerussite sheet’s Distribution opens in Sweden and gives five British places. From Långban, Värmland, Sweden. At Tvedalen, near Larvik, Norway. In England, relatively abundant on the Higher Pitts Farm, Mendip Hills, and as large crystals in the Merehead quarry, near Shepton Mallet, Somerset; at many mines in Caldbeck Fells, Cumbria. From Wanlockhead, Dumfriesshire, and Leadhills, Lanarkshire, Scotland (Leadhills and Wanlockhead). At the Kamariza mine, Laurium, Greece. In the Ilímaussaq intrusion, Greenland. From Tsumeb, Namibia. In the Seh-Changi mine, near Neyband, Iran. At Mont Saint-Hilaire, Quebec. In the USA, exceptional crystals from the Mammoth-St. Anthony mine, Tiger, Arizona; the C & B mine, Gila Co.; and the Bunker Hill mine, Idaho.
What it grows with. The association line gives lead at Långban, and cerussite, leadhillite, matlockite, paralaurionite, diaboleite and galena at the Mammoth-St. Anthony mine. Hydrocerussite is also named as an associate on the sheets of mendipite and diaboleite in the Mendip ground. How to tell it from cerussite, the species it most often sits beside, is worked through at cerussite vs hydrocerussite.
Hydrocerussite is 80.14% lead by mass; lead is covered on toxic minerals in a collection, and this page is not health or safety advice. Related species are at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.