Boulangerite
Boulangerite is Pb5Sb4S11: dull lead-gray needles to 1 cm, brownish streak, hardness 2.5 to 3, density about 6.2. Where it sits among 10 lead–antimony sulfides.
Boulangerite is lead antimony sulfide, Pb5Sb4S11 on the September 2026 IMA list: monoclinic, dull lead-gray needles to 1 cm, brownish streak, hardness 2.5 to 3, density about 6.2, type locality Molières, France. Worked, it is 55.23% lead. Of ten IMA rows made of lead, antimony and sulfur alone, it is third from the lead-rich end.
In short
- The species. The Handbook of Mineralogy sheet gives needlelike monoclinic crystals to 1 cm, seldom terminated and strongly striated, also fibrous and compact masses; cleavage distinct on {100}; brittle, flexible in thin crystals; hardness 2.5 to 3; density about 6.2; dull lead-gray with a brownish streak. The September 2026 IMA-CNMNC Master List writes Pb5Sb4S11, status G, 1837, France.
- The lead–antimony ladder. A script finds 10 IMA rows whose formula holds only Pb, Sb and S. Ranked by lead atoms per antimony atom they run from fülöppite, 0.375 and 29.93% lead, to geocronite, 2.333 and 66.40%. Boulangerite, 1.250 and 55.23%, sits between semseyite, 1.125, and falkmanite, 1.500.
- Documented failure: the sheet’s ideal column. Worked from Pb5Sb4S11, ideal boulangerite is 55.23% lead, 25.97% antimony, 18.80% sulfur. The sheet prints 55.42, 25.69 and 18.89, read from the rendered PDF, and those do not come from that formula. Its two analyses do check: recalculated, the Cleveland mine gives Pb5.17 Fe0.14 Sb4.04 S11.00, as printed.
- Documented failure: weight. A 20.00 g piece reads 16.77 g in water. Semseyite reads 16.68 g, meneghinite 16.86 g, geocronite 16.90 g and owyheeite 16.78 to 16.93 g, all within 0.16 g. jamesonite, at 16.45 g, is 0.33 g lighter and can be split by weight; the boulangerite neighbours cannot.
- Where it is found. The sheet says widespread, only a few localities given: Molières [TL] and Saint-Pons, France; Bottino, Italy, in rings; Sala, Nasafjell and Boliden, Sweden; the Harz and Bavaria; Trepča; Příbram; Idaho, Montana and Colorado; Noche Buena, Mexico; and Madoc, Ontario, in rings. It names no British locality.
| Mineral | IMA formula; status, year, country | Pb per Sb (atoms) | Pb by mass | Sb by mass | Hardness | Density; 20.00 g in water | Streak (sheet) |
|---|---|---|---|---|---|---|---|
| Stibnite | Sb2S3; G, 1832, unknown | 0 | 0 | 71.69% | 2 | 4.63; 15.68 g | Lead-gray |
| Fülöppite | Pb3Sb8S15; G, 1929, Romania | 0.375 | 29.93% | 46.91% | 2.5 | 5.22; 16.17 g | Reddish gray |
| Zinkenite | Pb9Sb22S42; G, 1826, Germany | 0.409 | 31.66% | 45.48% | 3–3.5 | 5.33; 16.25 g | Steel-gray |
| Plagionite | Pb5Sb8S17; G, 1833, Germany | 0.625 | 40.55% | 38.12% | 2.5 | 5.54; 16.39 g | Blackish lead-gray, deep red-brown |
| Robinsonite | Pb4Sb6S13; G, 1952, USA | 0.667 | 41.94% | 36.97% | 2.5–3 | 5.64–5.75; 16.45–16.52 g | Not printed |
| Jamesonite (with Fe) | Pb4FeSb6S14; G, 1825, United Kingdom | 0.667 | 40.15% | 35.39% | 2.5 | 5.63; 16.45 g | Not printed |
| Heteromorphite | Pb7Sb8S19; G, 1849, Germany | 0.875 | 47.81% | 32.11% | 2.5–3 | 5.73; 16.51 g | Black |
| Plumosite | Pb2Sb2S5; Q, 1845, Germany | 1.000 | 50.65% | 29.76% | n.f. | n.f. | n.f. |
| Semseyite | Pb9Sb8S21; G, 1881, Romania | 1.125 | 53.10% | 27.73% | 2.5 | 6.03; 16.68 g | Black |
| Boulangerite | Pb5Sb4S11; G, 1837, France | 1.250 | 55.23% | 25.97% | 2.5–3 | ~6.2; 16.77 g | Brownish |
| Falkmanite | Pb3Sb2S6; G, 1940, Germany | 1.500 | 58.78% | 23.03% | n.f. | n.f. | n.f. |
| Geocronite | Pb14Sb6S23; G, 1840, Sweden | 2.333 | 66.40% | 16.72% | 2.5 | 6.46; 16.90 g | Pale lead-gray to grayish blue |
What is boulangerite? Lead-gray needles of lead antimony sulfide
Boulangerite is Pb5Sb4S11, a lead-gray sulfosalt that grows as fine needles and fibrous or compact masses, with a brownish streak. The Handbook of Mineralogy boulangerite sheet gives monoclinic needlelike crystals, point group 2/m, to 1 cm, rarely as tiny rings; crystals are seldom terminated and strongly striated along [001]. Cleavage is distinct on {100}; it is brittle, but flexible in thin crystals; hardness 2.5 to 3; density about 6.2 measured and 6.21 calculated. It is dull lead-gray, metallic and may be silky.
What the IMA list records. Boulangerite, Pb5Sb4S11, status G (grandfathered), 1837, France. The sheet marks Molières, Gard, as the type locality and names it for Charles Louis Boulanger (1810–1849), a French mining engineer who called attention to the species; see what a type locality is.
Where it forms. In hydrothermal veins formed at low to medium temperatures, with lead sulfosalts, galena, stibnite, sphalerite, pyrite, arsenopyrite, siderite and quartz (sheet).
Where does boulangerite sit among lead–antimony sulfides? The ladder
The lead–antimony ladder: of the 10 IMA rows written in lead, antimony and sulfur alone, boulangerite has the third-highest ratio of lead to antimony, 5 to 4. A field scan of the September 2026 list for formulas of the form Pb, Sb, S, checked by a whole-line token scan, finds the same 10. In order of lead per antimony atom they are fülöppite 0.375, zinkenite 0.409, plagionite 0.625, robinsonite 0.667, heteromorphite 0.875, plumosite 1.000, semseyite 1.125, boulangerite 1.250, falkmanite 1.500 and geocronite 2.333. Lead by mass rises with the ratio, from 29.93% to 66.40%; boulangerite is 55.23%.
Documented failure: the sheet’s ideal column. The boulangerite sheet prints its ideal Pb5Sb4S11 as Pb 55.42, Sb 25.69, S 18.89. Worked from standard atomic weights the formula gives 55.23, 25.97 and 18.80, so the printed column is 0.19 high in lead and 0.28 low in antimony. The rendered PDF shows the same figures as the text layer, so this is not an extraction error. The two analyses do reproduce: Cleveland mine, Pb5.17 Fe0.14 Sb4.04 per 11 sulfur; Boliden, Pb5.05 with 3.75 antimony and 0.28 bismuth. This page uses the worked figures.
A questionable rung. Plumosite, Pb2Sb2S5, is on the list with status Q, which the list defines as poorly characterized minerals whose validity could be doubtful. No Handbook sheet for it could be fetched, so the ladder gives only its formula numbers.
Boulangerite or jamesonite? Weight, streak and needle length
Boulangerite is about 0.33 g heavier in water than jamesonite for a 20.00 g piece, and its sheet prints a brownish streak where jamesonite’s prints none. jamesonite, Pb4FeSb6S14, density 5.63, reads 16.45 g; boulangerite, about 6.2, reads 16.77 g. The jamesonite sheet gives crystals to 10 cm and cleavage good on {001}; boulangerite’s gives needles to 1 cm and cleavage distinct on {100}. Hardness, 2.5 against 2.5 to 3, does not separate them. Methods: how to measure specific gravity at home and how to use a streak plate.
Documented failure: the heavier neighbours. Semseyite reads 16.68 g, 0.09 g lighter; meneghinite 16.86 g, 0.08 g heavier; geocronite 16.90 g; and owyheeite 16.78 to 16.93 g, a range that starts 0.01 g from boulangerite. Semseyite and heteromorphite print black streaks and geocronite pale lead-gray to grayish blue, against boulangerite’s brownish, but a streak colour is a judgement, and an analysis is what fixes the name.
Stibnite. stibnite, Sb2S3, is the antimony end with no lead: density 4.63, 15.68 g in water, lead-gray streak, highly flexible. Its sheet’s associates include lead sulfantimonides without naming boulangerite; the boulangerite sheet names stibnite among its associates.
Where is boulangerite found?
The boulangerite sheet calls it widespread and gives only a few localities. In France, Molières, Gard [TL], and Saint-Pons, Alpes-de-Haute-Provence; in rings from Bottino, Tuscany, Italy; in crystals from Sala, Västmanland, Nasafjell, Lappland, and Boliden, Västerbotten, Sweden; Wolfsberg in the Harz, Ober-Lahr near Altenkirchen, and Waldsassen, Bavaria, Germany; Trepča, Serbia; Příbram, Czech Republic; in the USA, the Coeur d’Alene and Wood River districts, Idaho, the Iron Mountain mine, Superior, Montana, and Augusta Mountain, Colorado; the Noche Buena mine, Mazapil, Zacatecas, Mexico; and Madoc, Ontario, as rings. It names no British locality.
What grows with it. The Association line names quartz and siderite but neither fluorite nor calcite, so whether a needle seen inside fluorite or calcite is boulangerite is not something the sheet settles. No USGS or BGS text was fetched, so this page makes no ore or use claim. Boulangerite is 55.23% lead by mass; see toxic minerals in a collection, which is not advice. More sulfide pages are at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.