Caledonite
Caledonite is Pb5Cu2(SO4)3(CO3)(OH)6: verdigris to blue-green, pale green streak, hardness 2.5 to 3, density 5.6 to 5.76. Telling it from linarite, worked.
Caledonite is a lead copper sulphate-carbonate, Pb5Cu2(SO4)3(CO3)(OH)6, named from Caledonia, the Roman name for Scotland: orthorhombic, deep verdigris-green to blue-green, streak pale green, hardness 2.5 to 3, measured density 5.6 to 5.76. Linarite, its azure-blue companion at Leadhills, has a pale blue streak and twice the copper share.
In short
- Named for Scotland. The September 2026 IMA-CNMNC Master List lists caledonite as Cu2Pb5(SO4)3(CO3)(OH)6, status G, 1832, United Kingdom. The Handbook of Mineralogy sheet writes Pb5Cu2(SO4)3(CO3)(OH)6 and derives the name from the Latin Caledonia, the first known locality being in Scotland. It names Leadhills and Wanlockhead.
- The 16 g line. In the table’s six blue and green minerals, a 20.00 g piece reads 16.26 to 16.66 g in water when it carries lead (caledonite, linarite, chenite) and 14.70 to 15.06 g when it is copper only (azurite, brochantite, malachite). The gap is 1.20 g. Above 16 g, a blue-green piece from this suite is a lead-copper mineral.
- Then streak and colour. Caledonite: verdigris-green to blue-green, streak pale green. Linarite: bright to dark azure-blue, streak pale blue. Chenite: sky-blue, streak pale blue. Weight cannot separate these three: caledonite sits 0.17 to 0.27 g above linarite and 0.13 to 0.23 g below chenite.
- Copper share, worked. On standard atomic weights caledonite is 64.22% lead and 7.88% copper; linarite, PbCu(SO4)(OH)2, is 51.69% lead and 15.85% copper, twice the copper share. Five lead atoms to two copper against one to one. The oxide columns match both sheets’ ideal analyses.
- A Leadhills classic, also at Red Gill. The sheet says caledonite is widely distributed, but fine specimens are uncommon. It names Leadhills, Wanlockhead and Red Gill in Caldbeck Fells in Britain, and large crystals from Tchah Milleh, Iran, the Mammoth-St. Anthony mine, Arizona, and the Blue Bell mine, California.
| Species | IMA formula | Lead? | System (Handbook) | Colour (Handbook) | Streak | Hardness | Density | 20.00 g piece in water | Leadhills on the sheet |
|---|---|---|---|---|---|---|---|---|---|
| Caledonite | Cu2Pb5(SO4)3(CO3)(OH)6 | Yes | Orthorhombic | Deep verdigris-green, blue-green | Pale green | 2.5 to 3 | 5.6 to 5.76 | 16.43 to 16.53 g | Leadhills and Wanlockhead |
| Linarite | PbCu(SO4)(OH)2 | Yes | Monoclinic | Bright to dark azure-blue | Pale blue | 2.5 | 5.35 | 16.26 g | Leadhills |
| Chenite | CuPb4(SO4)2(OH)6 | Yes | Triclinic | Sky-blue | Pale blue | About 2.5 | 5.98 | 16.66 g | Susanna mine, Leadhills |
| Malachite | Cu2(CO3)(OH)2 | No | Monoclinic | Bright green, dark green, blackish green | Pale green | 3.5 to 4 | 4.05 | 15.06 g | Not named |
| Brochantite | Cu4(SO4)(OH)6 | No | Monoclinic | Emerald-green, blackish green, pale green | Pale green | 3.5 to 4 | 3.97 | 14.96 g | Not named |
| Azurite | Cu3(CO3)2(OH)2 | No | Monoclinic | Azure-blue, Berlin blue, very dark to pale blue | Pale blue | 3.5 to 4 | 3.773 | 14.70 g | Not named |
What is caledonite? A lead copper sulphate named for Scotland
The names. The September 2026 IMA-CNMNC Master List gives Cu2Pb5(SO4)3(CO3)(OH)6, status G, 1832, United Kingdom; the Handbook sheet writes Pb5Cu2(SO4)3(CO3)(OH)6. The atoms are identical; only the order differs. The sheet’s Name field: from the Latin Caledonia, the Roman name for the Highlands of Scotland, the first known locality. Type material is recorded at the Natural History Museum, Paris. Caledonite is one of 7 rows that the IMA list dates G, 1832, with the United Kingdom as country; leadhillite and lanarkite are two others.
Is caledonite a crystal or a mineral? A mineral species, which grows as crystals: striated prismatic crystals to 2.5 cm, typically flattened and showing many forms, in divergent aggregates, rarely fibrous, and as massive coatings. The cleavage is perfect on {010}, with two imperfect directions; the fracture is uneven and the mineral brittle. The sheet also records it as piezoelectric. The distinction is set out on crystal vs mineral.
Composition, worked on standard atomic weights: formula mass 1613.31; 64.22% lead and 7.88% copper by mass. As oxides, 69.17% PbO, 9.86% CuO, 14.89% SO3, 2.73% CO2 and 3.35% H2O, the sheet’s ideal column. Its analysis from Challacollo, Chile, corresponds to Pb5.06Cu2.00, very close to the ideal five to two.
Caledonite or linarite? Streak first, then copper
Both are blue lead-copper sulphates of the oxidised zone, both are on each other’s association lists, and both sheets name Leadhills and Caldbeck Fells. Their sheets separate them three ways. Colour: caledonite deep verdigris-green to blue-green; linarite bright to dark azure-blue, with pleochroism to Prussian blue. Streak: pale green against pale blue, on a streak plate. Structure: caledonite orthorhombic, linarite monoclinic with crystals to 8 cm.
Copper, worked. Linarite, PbCu(SO4)(OH)2, formula mass 400.82, is 51.69% lead and 15.85% copper: one lead atom to one copper, where caledonite has five to two. By mass, caledonite carries 8.15 parts of lead per part of copper, linarite 3.26. Linarite’s oxide column, 55.69% PbO and 19.85% CuO, matches its sheet.
Documented negative: weight and hardness. A 20.00 g piece reads 16.43 to 16.53 g in water as caledonite and 16.26 g as linarite, 0.17 to 0.27 g apart; hardness is 2.5 to 3 against 2.5. Chenite, sky-blue with a pale blue streak, reads 16.66 g, only 0.13 to 0.23 g above caledonite. Leadhills crystals are typically small, as the Leadhills and Wanlockhead page notes, which makes even that gap hard to read. Colour and streak decide, not the scale; the method is on how to measure specific gravity at home.
Is it caledonite, malachite or brochantite? The 16 g line
The rule: a 20.00 g blue or green piece reading above 16 g in water is a lead-copper mineral; below about 15.1 g, copper only. In the table, the three lead-copper sulphates read 16.26 to 16.66 g and the three copper minerals, all on caledonite’s association list, 14.70 to 15.06 g. The gap is 1.20 g, 120 steps on a 0.01 g balance.
Why it is needed. Caledonite’s pale green streak is shared by malachite and brochantite, and its blue-green colour overlaps both. Hardness hints but does not decide: 2.5 to 3 against 3.5 to 4. Weight does, because five lead atoms in the formula lift the density to 5.6 to 5.76, against 3.97 for brochantite and 4.05 for malachite.
Where the line fails. It needs a clean piece of 20 g or so; a thin crust on matrix weighs the matrix. It also says nothing between the three lead-copper minerals. Blue azurite reads 14.70 g, so among the minerals in the table a blue piece above 16 g is linarite or chenite rather than azurite. Other blue lead-copper minerals, such as boleite, are compared on boleite.
Where caledonite is found: Leadhills, Red Gill and Arizona
The Distribution field opens widely distributed, although fine specimens are uncommon. In Scotland it names Leadhills, Lanarkshire, and Wanlockhead, Dumfriesshire; in England, Red Gill and other mines, Caldbeck Fells, Cumbria. The live Leadhills and Wanlockhead page lists caledonite among the district’s classics, and leadhillite is on its association list.
Large crystals, per the sheet, come from Tchah Milleh, Anarak, Iran; the Mammoth-St. Anthony mine, Tiger, Arizona, in rich masses; and the Blue Bell mine near Baker, California. It also names the Preobrazhensky mine, Beresovsk, in the Urals; the Rowley mine, Arizona; the Mex-Tex mine, New Mexico; the Chance mine and Cerro Gordo, California; Challacollo, Chile; and Paddy’s River mine, Australian Capital Territory.
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.