Duftite
Duftite, PbCu(AsO4)(OH): an olive-green orthorhombic lead copper arsenate, adelite group, hardness 4.5, density 6.40, abundant at Tsumeb, Namibia (sheet).
Duftite is a lead copper arsenate, PbCu(AsO4)(OH) on the IMA list (G, 1920, Namibia), in the adelite group with conichalcite. Its Handbook sheet gives olive-green to grey-green orthorhombic crystals to 5 mm, usually crusts, hardness 4.5, density 6.40, and calls it abundant at Tsumeb. Lead for calcium is the difference from conichalcite: 1.49 g in water on 20 g.
In short
- Formula and status. The September 2026 IMA-CNMNC Master List gives PbCu(AsO4)(OH), status G, 1920, Namibia; the Handbook of Mineralogy sheet writes the same and files it in the adelite group. Worked on standard atomic weights: formula mass 426.67, lead 48.56%, copper 14.89%, arsenic 17.56%; as oxides PbO 52.31, CuO 18.64, As2O5 26.93 and H2O 2.11, the sheet’s column (3).
- The 1.49 g line. Conichalcite is CaCu(AsO4)(OH): the same adelite-group formula with calcium where duftite has lead. On the two sheets’ measured densities, 6.40 and 4.33, a 20.00 g piece reads 16.88 g in water as duftite and 15.38 g as conichalcite, 1.49 g apart, enough for a hydrostatic balance reading to 0.01 g.
- Documented failure: mottramite sits inside the margin. Mottramite, PbCu(VO4)(OH), carries the same lead and copper with vanadate for arsenate. At its sheet’s “about 5.9” it reads 16.61 g, 0.27 g from duftite, and both sheets list olive-green and crusts. Weighing separates duftite from conichalcite, not from mottramite.
- The lead-site check. The sheet’s two Tsumeb analyses recast to 0.992 and 0.998 Pb with 0.059 and 0.071 Ca per arsenic: calcium is about 6% of the lead-plus-calcium site, so both are duftite, not conichalcite. The sheet’s cell reproduces its D(calc.) exactly, 6.602; the measured 6.40 sits 0.20 lower and the page reports both.
- Where, and “on calcite”. Abundant at Tsumeb, Namibia, rarely in large crystals, where the sheet lists olivenite, mottramite, azurite, malachite, wulfenite and calcite as associates. Also Zambia, Morocco, France, Germany, Russia, Mexico, the USA, Australia and, in England, Brandy Gill, Caldbeck Fells, and the Penberthy Croft mine, Cornwall.
| Mineral | IMA formula | Group (sheet) | System | Hardness | Density (meas.) | 20.00 g in water | Streak | Pb / Cu / As by mass |
|---|---|---|---|---|---|---|---|---|
| Duftite | PbCu(AsO4)(OH); G, 1920, Namibia | Adelite | Orthorhombic | 4.5 | 6.40 | 16.88 g | Pale green to white | 48.56 / 14.89 / 17.56% |
| Conichalcite | CaCu(AsO4)(OH); G, 1849, Spain | Adelite | Orthorhombic | 4.5 | 4.33 | 15.38 g | Green | 0 / 24.48 / 28.87% |
| Mottramite | PbCu(VO4)(OH); G, 1876, United Kingdom | Descloizite | Orthorhombic | 3–3.5 | about 5.9 | 16.61 g | Yellowish green | 51.45 / 15.78 / 0% |
| Tsumebite | Pb2Cu(PO4)(SO4)(OH); G, 1912, Namibia | Brackebuschite | Monoclinic | 3.5 | 6.01–6.13 | 16.67–16.74 g | Not printed | 60.41 / 9.26 / 0% |
| Duftite, Tsumeb analysis (1) | Recast per As: Pb 0.992, Ca 0.059, Cu 1.073, Zn 0.025 | — | — | — | — | — | — | 46.51 / 15.43 / 16.96% (worked from oxides) |
| Duftite, cell check | P212121, a 7.768, b 9.211, c 5.999 Å, Z = 4, V 429.23 ų | — | — | — | 6.602 from cell = printed calc. | 16.97 g at 6.602 | — | — |
What is duftite? A lead copper arsenate of the adelite group
The formula. The September 2026 IMA list gives PbCu(AsO4)(OH), status G, 1920, Namibia. The Handbook of Mineralogy duftite sheet writes the same and places it in the adelite group. Worked, lead is 48.56%, copper 14.89% and arsenic 17.56% by mass, and the sheet’s ideal column, PbO 52.31, CuO 18.64, As2O5 26.93 and H2O 2.11, reproduces exactly.
What the sheet describes. Orthorhombic, point group 222, space group P212121 (from synthetic material). Crystals may be pseudo-octahedral, or elongated along [001], commonly curved and rough, to 5 mm; usually in crusts and aggregates. Conchoidal fracture, hardness 4.5; no cleavage is printed. Bright olive-green to grey-green, pale apple-green in transmitted light and generally zoned due to compositional variations; streak pale green to white; lustre dull to vitreous on fractures. Biaxial (−), α 2.03 to 2.04, β 2.06 to 2.08, γ 2.08 to 2.10, 2V large. Other arsenates are in the species index.
Duftite or conichalcite? Lead for calcium, weighed
The relation. Both sheets file their mineral in the adelite group and both are orthorhombic P212121 with hardness 4.5. By IMA formula, duftite is PbCu(AsO4)(OH) and conichalcite CaCu(AsO4)(OH): one swap, lead for calcium, which makes the duftite formula 1.64 times as heavy. The sheets’ measured densities follow: 6.40 against 4.33.
The 1.49 g line. A 20.00 g piece reads 16.88 g in water as duftite and 15.38 g as conichalcite, so a reading near 16.9 g points to duftite and one near 15.4 g to conichalcite; the method is on how to measure specific gravity at home. Colour does less: duftite’s sheet gives bright olive-green to grey-green, conichalcite’s grass-green to yellowish green and pistachio-green, and the streaks, pale green to white against green, are both greenish. The live conichalcite page puts duftite as the heavy outlier among the green arsenate crusts; the numbers here agree with it.
Duftite or mottramite? Where weighing fails
Documented failure. Mottramite is PbCu(VO4)(OH): duftite’s lead and copper with vanadate in place of arsenate. Its sheet prints density about 5.9, which reads 16.61 g in water for 20.00 g, 0.27 g from duftite’s 16.88 g; with an approximate density on one side, that margin does not settle a crust. Mottramite’s sheet gives hardness 3 to 3.5 and a yellowish green streak against duftite’s 4.5 and pale green to white, but both sheets list olive-green and crusts, and the duftite sheet lists mottramite as an associate at Tsumeb, so the two can share a specimen. Only an analysis that finds arsenic or vanadium settles it. The mottramite series with descloizite is on the mottramite page and not repeated here.
The lead-site check, from the sheet. Analysis (1), Tsumeb, prints SiO2 0.44, As2O5 26.01, CuO 19.32, ZnO 0.46, PbO 50.10, CaO 0.75, H2O+ 2.65, H2O− 0.08, total 99.81. Per arsenic atom that is Pb 0.992, Ca 0.059, Cu 1.073 and Zn 0.025; analysis (2), also Tsumeb, gives Pb 0.998 and Ca 0.071. Calcium is 5.6% and 6.6% of the lead-plus-calcium site: both analyses are duftite. The sheet cites a 1980 study titled solid solution in the adelite group of arsenates; this page draws nothing from the title beyond what the analyses show.
How dense is duftite? The cell against the balance
Worked. The sheet’s cell, a 7.768, b 9.211, c 5.999 Å, gives V = 429.23 ų; with Z = 4 and the IMA formula, Z·M·1.66054/V = 6.602, the printed D(calc.) to the third decimal. The measured value is 6.40, 0.20 (3.1%) lower; a 20.00 g piece reads 16.97 g in water at the calculated density and 16.88 g at the measured one. The sheet does not explain the gap, and its own analyses carry silica, zinc and calcium that the ideal formula does not.
Why it matters. The 1.49 g line uses measured densities on both sides. Using duftite’s calculated value would widen the gap to conichalcite to 1.59 g; the page uses the measured figures because that is what a balance meets.
Where duftite is found, and duftite on calcite
Occurrence and associates. An uncommon mineral in the oxidized zone of some hydrothermal base-metal deposits. The sheet lists two association lines: olivenite, mottramite, azurite, malachite, wulfenite and calcite at Tsumeb, Namibia; and bayldonite, beudantite, mimetite and cerussite at the Cap Garonne mine, France. “Duftite on calcite” is therefore a Tsumeb association the sheet records; the sheet says nothing about which mineral grows on which.
Distribution, as printed. Many minor localities. Abundant at Tsumeb, Namibia, rarely in large crystals; Fitula and Mufulira, Zambia; the Touissit mine, near Oujda, Morocco; the Cap Garonne mine, Var, France; the Virneberg mine, near Rheinbreitbach, Germany; Beresovsk, Middle Urals, Russia; in England, Brandy Gill, Caldbeck Fells, Cumbria, and the Penberthy Croft mine, St. Hilary, Cornwall; the Ojuela mine, Mapimí, Durango, Mexico; in the USA, the Mohawk and Belmont mines, California, the Black Pine mine, Montana, and Granite Gap, New Mexico; in Australia, large crystals in the Mt. Bonnie mine, Northern Territory, and Broken Hill, New South Wales, and the Puttapa zinc mine and the Mt. Malvern mine, South Australia. Named in honour of G. Duft, General Manager of the mine at Tsumeb; the sheet marks no type locality (see what is a type locality). Tsumebite is another species named from the same mine.
Hazard, in one line. Duftite is 48.56% lead and 17.56% arsenic by formula; hazard questions are routed to toxic minerals in a collection and the lead arsenate page is mimetite toxic, and this is not advice. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.