Leadhillite
Leadhillite is Pb4(SO4)(CO3)2(OH)2: hardness 2.5 to 3, density 6.55, pearly basal cleavage. Two other minerals share its formula; a scale cannot split them.
Leadhillite is a lead sulphate-carbonate, Pb4(SO4)(CO3)2(OH)2, named for Leadhills in Scotland: monoclinic, commonly twinned into pseudohexagonal groups, hardness 2.5 to 3, measured density 6.55, with a perfect basal cleavage that is pearly. It is 76.82% lead by mass. Susannite and macphersonite have the same formula, so leadhillite is one of three IMA trimorphs.
In short
- Named for the place. The September 2026 IMA-CNMNC Master List lists leadhillite as Pb4(SO4)(CO3)2(OH)2, status G, 1832, United Kingdom; the Handbook of Mineralogy sheet prints the same formula and names it for its initially-noted occurrence at Leadhills. Type material is recorded at the Natural History Museum, Paris.
- One formula, three minerals. A script over the IMA list finds 3 rows with the formula Pb4(SO4)(CO3)2(OH)2: leadhillite (G, 1832), susannite (G, 1845) and macphersonite (A, 1982-105). The Handbook calls them trimorphous. All three sheets name Leadhills.
- The 0.25 g trap. Seven white lead minerals recorded at Leadhills, from leadhillite to cerussite and lanarkite, read between 16.86 and 17.11 g in water for a 20.00 g piece. The three trimorphs sit within 0.03 g of each other. The scale does not identify leadhillite here.
- UV does not either. On a ligature-aware search of the seven sheets, 6 print a yellow fluorescence; susannite’s prints none. What the sheets do separate is habit: leadhillite’s perfect, pearly basal cleavage and sectile tenacity against cerussite’s very brittle crystals.
- Lead, worked. On standard atomic weights the formula is 76.82% lead, and its oxide form, 82.75% PbO, 7.42% SO3, 8.16% CO2 and 1.67% H2O, is the sheet’s ideal column exactly. Lead minerals and handling are covered on toxic minerals in a collection and is galena toxic; this page gives no health or handling advice, and none of it is advice.
| Species | IMA formula | IMA status, year | System (Handbook) | Hardness | Density | 20.00 g piece in water | Fluorescence on the sheet | Leadhills on the sheet |
|---|---|---|---|---|---|---|---|---|
| Leadhillite | Pb4(SO4)(CO3)2(OH)2 | G, 1832 | Monoclinic, pseudorhombohedral | 2.5 to 3 | 6.55 | 16.95 g | May fluoresce pale yellow under UV | Leadhills and Wanlockhead |
| Susannite | Pb4(SO4)(CO3)2(OH)2 | G, 1845 | Hexagonal, point group 3 | Not determined | 6.52 calculated only | 16.93 g | None printed | Susanna mine, Leadhills |
| Macphersonite | Pb4(SO4)(CO3)2(OH)2 | A, 1982-105 | Orthorhombic, pseudohexagonal | 2.5 to 3 | 6.50 to 6.55 | 16.92 to 16.95 g | May show bright yellow, SW and LW | Leadhills |
| Cerussite | Pb(CO3) | G, 1845 | Orthorhombic | 3 to 3.5 | 6.55 | 16.95 g | May fluoresce yellow, LW | Leadhills |
| Anglesite | Pb(SO4) | G, 1832 | Orthorhombic | 2.5 to 3 | 6.38 | 16.87 g | May fluoresce yellow under UV | Leadhills and Wanlockhead |
| Lanarkite | Pb2O(SO4) | G, 1832 | Monoclinic | 2 to 2.5 | 6.92 | 17.11 g | Fluoresces yellow, X-rays and LW | Susanna mine; Meadowfoot smelter slag |
| Scotlandite | Pb(S4+O3) | A, 1982-001 | Monoclinic | About 2 | 6.37 | 16.86 g | May fluoresce yellow, LW | A museum specimen labelled Susanna mine |
What is leadhillite? A lead sulphate-carbonate named for Leadhills
The names. The September 2026 IMA-CNMNC Master List gives leadhillite the formula Pb4(SO4)(CO3)2(OH)2, status G, year 1832, with the United Kingdom as the country of first description. The Handbook sheet prints the same formula and says the name is for its initially-noted occurrence at Leadhills, Scotland. The village and its neighbour have their own page, Leadhills and Wanlockhead.
What it looks like. Crystals to 13 cm, thick to thin tabular, may be barrel-shaped or pseudorhombohedral, with over 40 forms noted; also granular and massive. Twinning is very common and gives pseudohexagonal groupings, so a monoclinic mineral often looks hexagonal. The cleavage is perfect on {001}, the plate face, where the lustre turns pearly; elsewhere it is resinous to adamantine. The sheet calls it sectile. Colours run from colourless, white and grey through pale yellow, pale green and pale blue to brown.
Composition, worked on standard atomic weights (Pb 207.2, S 32.06, C 12.011, O 15.999, H 1.008): formula mass 1078.89, of which lead is 76.82%. As oxides that is 82.75% PbO, 7.42% SO3, 8.16% CO2 and 1.67% H2O, the sheet’s ideal column to the hundredth. Its one analysis, from Granby, Missouri, gives 82.44% PbO. The sheet adds that it is decomposed by hot water.
Leadhillite, susannite or macphersonite? Three minerals, one formula
The IMA count. Parsing every row of the September 2026 list and matching the formula column exactly, 3 rows read Pb4(SO4)(CO3)2(OH)2; a raw line scan finds the same 3. They are leadhillite, G, 1832; susannite, G, 1845; and macphersonite, A, IMA 1982-105. All three give the United Kingdom as country. The Handbook sheets call them trimorphous: same composition, three structures.
How the sheets separate them. By symmetry: leadhillite is monoclinic, pseudorhombohedral; macphersonite orthorhombic, pseudohexagonal, in thin to tabular crystals to 1 cm; susannite hexagonal, point group 3, in equant to acute rhombohedral crystals to 8 cm. The susannite sheet says its powder pattern is nearly identical to leadhillite’s and that it may be distinguished by the presence of a diffraction peak at 6.5. That is a laboratory test, not a hand test. The susannite sheet also records it as formed at temperatures above 80 °C.
Documented negative: the scale. A 20.00 g piece reads 16.95 g in water as leadhillite, 16.92 to 16.95 g as macphersonite and 16.93 g as susannite, the last from a calculated density because the sheet has no measured one. The spread is 0.03 g. The method is on how to measure specific gravity at home, and here it cannot help. Macphersonite honours Harry Gordon Macpherson, Keeper of Minerals at the Royal Scottish Museum, where type material is held; its IMA number is 1982-105, so a label written before then cannot carry the name.
Leadhillite or cerussite? The 0.25 g trap
Seven white lead minerals, one narrow band. Every sheet in the table above names Leadhills or Wanlockhead. Worked as 20 − 20/D, a 20.00 g piece of any of them reads between 16.86 g (scotlandite) and 17.11 g (lanarkite) in water: 0.25 g from end to end. Leadhillite and cerussite, both 6.55, read the same 16.95 g. Anglesite is 0.08 g lighter. A density reading proves the piece is a dense lead mineral; it does not say which.
UV is no better. A case-insensitive, ligature-aware search of the seven sheets, with hemimorphite and willemite as positive controls, finds a yellow fluorescence printed on 6: leadhillite, macphersonite, cerussite, anglesite, lanarkite and scotlandite, each with may or a stated wavelength. Only susannite’s sheet prints none. The general lamp question is on fluorescent minerals explained.
What does separate them is in the sheets’ habit fields. Leadhillite: tabular plates, a perfect cleavage on the plate face with a pearly lustre there, sectile. Cerussite: very brittle, adamantine, with stellate and reticulated twins. Anglesite: brittle, typically elongated prismatic, sometimes banded around a galena core. Lanarkite: crystals elongated in one direction, flexible in thin laminae. These are observations to make with a lens, not tests to perform on the specimen.
Where leadhillite is found: Leadhills, Caldbeck Fells and Tsumeb
In Scotland the Distribution field names Leadhills, Lanarkshire, and Wanlockhead, Dumfriesshire, and the Drumruck mine, Kirkcudbrightshire. The Leadhills association it gives is cerussite, anglesite, lanarkite, caledonite and linarite; the blue-green companion has its own page, caledonite.
Elsewhere, per the sheet: Caldbeck Fells, Cumbria; Penberthy Croft, St. Hilary, and the Greystone quarry, Levant, Cornwall; Bleiberg, Austria; the Beer Cellar mine, Granby, Missouri; the Tintic district, Utah; fine crystals from the Mammoth-St. Anthony mine, Tiger, Arizona, and also the Rowley and Grand Reef mines and Bisbee; Leadville, Colorado; very large crystals from Tsumeb, Namibia; and Dundas, Tasmania. A few other localities are known, it ends; we add none.
Lead minerals and handling are covered on toxic minerals in a collection and is galena toxic; this page gives no health or handling advice, and none of it is advice. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.