Vauquelinite
Vauquelinite is CuPb2(CrO4)(PO4)(OH), green to brown, hardness 2.5 to 3, density 6.16. It is 7.37% chromium and shares four named localities with crocoite.
Vauquelinite is a lead copper chromate-phosphate, CuPb2(CrO4)(PO4)(OH), monoclinic, hardness 2.5 to 3 and density 6.16, green to brown with a greenish to brownish streak. The IMA list gives 1818 and Russia. It is crocoite's companion: each species' Handbook sheet names the other as an associate. It is 7.37% chromium by mass, against crocoite's 16.09%.
In short
- Vauquelinite and crocoite belong together. The Handbook of Mineralogy lists crocoite as vauquelinite's first associate at Beresovsk, and vauquelinite among crocoite's associates. Four of vauquelinite's localities are also on the crocoite sheet: the Tsvetnoi mine at Beresovsk, Obercallenberg in Saxony, the Argent mines in the Transvaal, and two mines south of Wickenburg, Arizona.
- Against the 176 sheets in this site's reference set, crocoite is the only one with chromium in its formula. Vauquelinite's own sheet is not in the set and is not counted. It carries half crocoite's chromium: 7.37% against 16.09%, calculated below.
- Hardness and density will not separate it from crocoite: 2.5 to 3 for both, and 6.16 against 6.0 to 6.1. Colour and streak will: vauquelinite is green to brown with a greenish to brownish streak; crocoite is hyacinth-red to orange with a yellow-orange streak.
- The real look-alike is mottramite, PbCu(VO4)(OH): grass-green, olive-green and siskin-green, density about 5.9, streak yellowish green. Chromium and phosphorus against vanadium is a question for an analysis. Mottramite is compared in detail on the descloizite page.
- The name honours Louis Nicolas Vauquelin, 1763 to 1829, the French chemist whom the Handbook credits with discovering chromium.
| Species | Formula | Hardness | Density | Colour on the sheet | Streak | Cr by mass |
|---|---|---|---|---|---|---|
| Vauquelinite | CuPb2(CrO4)(PO4)(OH) | 2.5 to 3 | 6.16 | Apple-green, siskin-green, olive-green, canary-yellow, brown, nearly black | Greenish to brownish | 7.37% |
| Crocoite | PbCrO4 | 2.5 to 3 | 6.0 to 6.1 | Hyacinth-red, red-orange, orange | Yellow-orange | 16.09% |
| Mottramite | PbCu(VO4)(OH) | 3 to 3.5 | About 5.9 | Grass-green, olive-green, yellow-green, siskin-green, blackish brown | Yellowish green | 0% in the formula |
| Duftite | PbCu(AsO4)(OH) | 4.5 | 6.40 | Bright olive-green to grey-green | Pale green to white | 0% |
| Pyromorphite | Pb5(PO4)3Cl | 3.5 to 4 | 7.04 | Dark grass-green, green, yellow, through orange and brown to colourless | White | 0% |
| Fornacite | CuPb2(CrO4)(AsO4)(OH) | No sheet consulted | No sheet consulted | No sheet consulted | No sheet consulted | 6.93% |
How is vauquelinite related to crocoite?
They are lead chromates of the same oxidised ores. Crocoite is PbCrO4; vauquelinite adds copper and a phosphate. The Handbook's vauquelinite analysis is from Beresovsk, the crocoite district of the Middle Urals, and its association line there reads crocoite, pyromorphite, mimetite, cerussite, beudantite and duftite. The crocoite sheet returns the compliment: phoenicochroite, vauquelinite and embreyite head its association list.
The shared localities, read from the two sheets side by side: the Tsvetnoi mine on Mt Uspenskaya in the Beresovsk district; Obercallenberg near Glauchau, Saxony; the Argent Pb–Zn mines about 100 km east of Johannesburg; and the Moon Anchor mine and the Potter-Kramer property south of Wickenburg, Maricopa County, Arizona. Four localities, counting the two Wickenburg mines as one.
The September 2026 IMA-CNMNC Master List gives vauquelinite 1818, Russia, and crocoite 1832, Russia; both are grandfathered. The crocoite sheet records exceptional specimens from the Dundas district of Tasmania; vauquelinite has no Tasmanian entry on its sheet, and neither Leadhills nor Cornwall, crocoite's two British localities, appears on the vauquelinite sheet.
What is vauquelinite made of? A worked calculation
The IMA writes CuPb2(CrO4)(PO4)(OH) and the Handbook Pb2Cu(PO4)(CrO4)(OH): two lead, one copper, one chromate, one phosphate and one hydroxyl in both, only in a different order. On standard atomic weights the formula mass is 705.91, and by mass that is 58.70% lead, 9.00% copper, 7.37% chromium and 4.39% phosphorus. The Handbook's ideal column, PbO 63.24, CuO 11.27, CrO3 14.16, P2O5 10.05, H2O 1.28, agrees within 0.01.
Chromium is rare in this site's reference set. Across its 176 sheets (method: pdftotext -layout, the header formula searched by regular expression for the element symbol Cr), only crocoite has chromium in its formula. Twelve others mention chromium, but only as a minor or trace constituent in an analysis, in a locality or reference title, or as the associate chromite.
Against crocoite. PbCrO4 has a formula mass of 323.19 and is 16.09% chromium and 64.11% lead, CrO3 30.94%, which is the Handbook's crocoite ideal column exactly. So vauquelinite carries 0.46 times crocoite's chromium: under half, the rest of the space taken by copper and phosphate.
The real Beresovsk analysis is not ideal. It reads CrO3 15.26% and P2O5 8.05%, with 1.09% Fe2O3. Converted to moles, that is 1.35 chromium to each phosphorus rather than 1 to 1. Why is not stated on the sheet, and we do not guess; the sheet does note that additional reported localities require modern confirmation, which is a reason to value an analysed specimen.
How to tell vauquelinite from mottramite, duftite and pyromorphite
Against crocoite the colour does the work, as the table shows. The difficult comparisons are with the other green lead-copper secondaries.
Mottramite, PbCu(VO4)(OH), is the closest. Its sheet colours overlap vauquelinite's almost term for term, grass-green, olive-green, siskin-green and blackish brown, and its density, about 5.9 measured and 6.187 calculated, sits near vauquelinite's 6.16. Hardness is half a point higher at 3 to 3.5, and the streak is yellowish green. The decision is chemical: chromium and phosphorus say vauquelinite, vanadium says mottramite. Mottramite's own sheet analysis carries 0.50% CrO3, a reminder that the two chemistries can meet. Mottramite is set against its zinc analogue on the descloizite page.
Duftite, PbCu(AsO4)(OH), is harder at 4.5 and denser at 6.40, pale green to white in streak, and it appears in vauquelinite's Beresovsk association. Pyromorphite is 3.5 to 4 and 7.04 with a white streak, and grows as hexagonal prisms, not wedge-shaped monoclinic crystals. See pyromorphite and how to use a streak plate.
Where vauquelinite is found
The sheet calls it a rare mineral in the oxidised zones of some hydrothermal base-metal deposits, as wedge-shaped crystals flattened on [100] to 5 mm, and as nodules, reniform crusts and granular or compact masses, twinned on {102}.
Its distribution: the Tsvetnoi mine, Mt Uspenskaya, Beresov district, near Yekaterinburg in the Middle Urals; in Germany, Öhrenstock near Ilmenau, Obercallenberg near Glauchau, and Reichenbach near Bensheim and Raidelbach in Hesse; the Exi mine near Laurium, Greece; the Mashamba West and Musonoi mines near Kolwezi and Kipushi in Katanga, Congo, the Musonoi material supplying the powder pattern; in Arizona, the Moon Anchor mine, the Rat Tail claim, the Potter-Kramer property, the Tonopah-Belmont mine, the Florence Lead-Silver mine and the Vanadinite mine; in Nevada, the Killie and Silver Coin mines; the Pequa mine in Pennsylvania; the Blue Bell mine in California; the Argent mines in the Transvaal; and Broken Hill, New South Wales. No British locality is recorded.
The rest of the lead secondaries are indexed at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.