Ferberite
Ferberite, Fe2+(WO4): the black iron tungstate at one end of the wolframite series, hardness 4 to 4.5, density 7.58, 60.54% tungsten, slightly magnetic.
Ferberite is iron tungstate, Fe2+(WO4) on the IMA list (grandfathered, 1863, Spain): monoclinic, black, hardness 4 to 4.5, density 7.58, 60.54% tungsten by mass and, on its Handbook sheet, slightly magnetic. It is the iron end of the series with hübnerite that collectors label wolframite, a name with no row on the IMA list.
In short
- The species. The September 2026 IMA-CNMNC Master List lists ferberite as Fe2+(WO4), status G, 1863, Spain. The Handbook of Mineralogy sheet gives monoclinic P2/c, wedge-shaped crystals to 15 cm, perfect {010} cleavage, hardness 4 to 4.5, density 7.58, black with a brownish black to black streak, slightly magnetic. Worked, FeWO4 is 60.54% tungsten; a 20.00 g piece reads 17.36 g in water.
- The cell, not the atom. Iron (55.845) and manganese (54.938) differ by 0.907 in atomic weight, so FeWO4 (303.68) is only 0.30% heavier than MnWO4 (302.77). The cells differ more: 133.44 cubic ångströms for ferberite, 138.39 for hübnerite, 3.71% larger. Worked, the densities are 7.558 and 7.266; FeWO4 in hübnerite’s cell would be 7.288. About 92.5% of the 0.292 gap is the cell.
- Documented failure: the printed densities. Neither sheet’s calculated density reproduces from its own cell: ferberite prints 7.60 against 7.558 worked (its cell is printed to two decimals, with β = 90°), hübnerite 7.234 against 7.266. The measured densities, 7.58 and 7.12 to 7.18, are 0.40 to 0.46 apart, more than the worked 0.29, so density points to an end of the series but does not assay a crystal.
- Wolframite and the series. The sheet says ferberite forms a series with hübnerite and that material approaching end-member composition is uncommon. Its Kurasawa, Japan, analysis is 99.2% iron of iron plus manganese, worked. Where a given analysis falls, and what a label should say, is on ferberite vs wolframite.
- Where, and the ore. The Distribution field names Panasqueira, Portugal; around Calstock and elsewhere in Cornwall; and, in the USA, “an ore mineral, well-crystallized”, from the Boulder Co. tungsten district, Colorado. The USGS 2021 Minerals Yearbook, Tungsten calls wolframite one of two principal minerals mined for tungsten.
| Row | Formula | Cell printed (Å, β) | Cell volume (ų) | Formula mass | Density worked | Density printed | 20.00 g piece in water |
|---|---|---|---|---|---|---|---|
| Ferberite | Fe2+(WO4) | a 4.72, b 5.70, c 4.96, β 90° | 133.44 | 303.68 | 7.558 | 7.58 meas.; 7.60 calc. | 17.36 g |
| Hübnerite | Mn2+(WO4) | a 4.8238, b 5.7504, c 4.9901, β 91.18° | 138.39 (+3.71%) | 302.77 (−0.30%) | 7.266 | 7.12–7.18 meas.; 7.234 calc. | 17.19–17.21 g |
| FeWO4 in hübnerite’s cell (arithmetic) | Fe2+(WO4) | Hübnerite’s | 138.39 | 303.68 | 7.288 | Not printed | — |
| MnWO4 in ferberite’s cell (arithmetic) | Mn2+(WO4) | Ferberite’s | 133.44 | 302.77 | 7.535 | Not printed | — |
| The gap, worked | — | — | Cell 3.71% | Atom 0.30% | 0.292, of which the cell 0.270 | Measured gap 0.40–0.46 | 0.15–0.17 g |
What is ferberite? Iron tungstate, Fe2+(WO4)
Ferberite is Fe2+(WO4) on the September 2026 IMA list, status G, grandfathered, 1863, with Spain as the country of first description. The first reference is the Neues Jahrbuch für Mineralogie, Geologie und Paläontologie (1863), page 641; the second, Inorganic Chemistry 63 (2024), 6898. The Handbook of Mineralogy ferberite sheet writes Fe2+WO4 and marks no type locality; the term is explained at what is a type locality.
What the sheet records. Monoclinic, point group 2/m, space group P2/c. Wedge-shaped crystals, typically flattened on {100} and elongated along [010] or, less commonly, along [001], to 15 cm, with faces striated parallel to [001] or [010]; also bladed groups and massive. Contact twins on {100} or {023}, more rarely {001}, and interpenetrant or lamellar twins. Cleavage {010} perfect, with partings on {100} and {102}; fracture uneven; brittle; hardness 4 to 4.5. Black, dark brown in transmitted light, nearly to entirely opaque; streak brownish black to black; lustre submetallic to metallic adamantine; biaxial (+), β about 2.40.
The analysis. Kurasawa, Yamanashi Prefecture, Japan: WO3 75.21, FeO 24.37, MnO 0.19, total 99.77, against the ideal FeWO4 column of 76.34 and 23.66, which the script reproduces exactly. Recast to four oxygens it is 0.987 tungsten, 1.032 iron and 0.008 manganese, and 59.64% tungsten by mass. The sheet places ferberite in high-temperature hydrothermal veins, greisens and granitic pegmatites, and residual in alluvial and eluvial deposits, with scheelite, topaz, fluorite, marcasite, pyrite, hematite and feldspar.
Why is ferberite heavier than hübnerite? The cell, not the atom
The atoms barely differ. Ferberite and hübnerite have the same formula shape, one iron or manganese, one tungsten and four oxygens, and the same space group, P2/c, with Z = 2. Iron is 55.845 and manganese 54.938 on standard atomic weights, so FeWO4 weighs 303.68 and MnWO4 302.77, 0.30% apart. That alone would make ferberite about 0.3% denser.
The cells do differ. Worked as abc·sin β, ferberite’s printed cell (a 4.72, b 5.70, c 4.96 Å, β 90°) is 133.44 cubic ångströms and hübnerite’s (a 4.8238, b 5.7504, c 4.9901 Å, β 91.18°) 138.39, 3.71% larger. The worked densities are 7.558 and 7.266, a gap of 0.292. Swap the formulas between the cells and the split is plain: FeWO4 in hübnerite’s cell is 7.288, 0.270 below ferberite, while MnWO4 in ferberite’s cell is 7.535, 0.023 below. Roughly 92.5% of the gap is the larger cell. The stolzite page shows the opposite case, where a heavier atom in nearly the same cell does the work.
Documented failure: the printed figures do not reproduce. Ferberite’s calculated density is printed as 7.60, but its own cell gives 7.558, 0.042 lower; the cell is printed to two decimals with β = 90°. This page reports the arithmetic and does not correct the sheet. Hübnerite’s printed 7.234 is 0.032 below its cell’s 7.266. The measured values, 7.58 for ferberite and 7.12 to 7.18 for hübnerite, are 0.40 to 0.46 apart. A 20.00 g piece reads 17.36 g in water as ferberite and 17.19 to 17.21 g as hübnerite, on the method at how to measure specific gravity at home; the same figures are on scheelite and is wolframite magnetic.
Is ferberite the same as wolframite?
Ferberite is a species; wolframite is a series name. A case-insensitive scan of the September 2026 IMA list finds 0 lines containing “wolfram”. The list carries ferberite and hübnerite, Mn2+(WO4), G, 1865, USA, and each sheet says it forms a series with the other. Webmineral’s wolframite page calls wolframite the group name for the hübnerite–ferberite series and records its IMA status as not approved.
How near the end member. The ferberite sheet’s Distribution field opens: “Numerous minor localities; material approaching end-member composition is uncommon.” The Kurasawa analysis is 99.2% iron of iron plus manganese, worked by atoms, the figure also on is wolframite magnetic. Where the iron–manganese line falls, how to read an analysis written as oxides, and what a label should say are on ferberite vs wolframite; the manganese end is on hübnerite.
Is ferberite magnetic? Does it fluoresce?
Slightly, on its sheet. The ferberite sheet’s physical properties end with the words “Slightly magnetic”; its reference 3 is Ülkü (1967) on the crystal and magnetic structure of ferberite. The hübnerite sheet prints no magnetic property. The laboratory separator figures for both, and why they do not place a crystal in the series, are on is wolframite magnetic and are not repeated here; the general picture is on which minerals are magnetic.
No fluorescence on the sheet. A ligature-aware search of the ferberite and hübnerite sheets for fluorescence, phosphorescence, luminescence and UV finds nothing; the positive controls, hemimorphite and willemite, both match. That agrees with scheelite, whose own shortwave response is on is scheelite fluorescent. A glow on a ferberite specimen is a reason to look at its associates, scheelite among them.
Where is ferberite found, and is it an ore of tungsten?
Distribution, as printed. Near Aquilas, Sierra de Almagrera, Almería Province, Spain; Panasqueira, Portugal; around Calstock and elsewhere in Cornwall, England; large crystals at Pechtelsgrün and Zinnwald, Saxony, Germany; Chanteloube, near Limoges, Haute-Vienne, France; in the USA, “an ore mineral, well-crystallized”, from a number of mines in the Boulder Co. tungsten district, Colorado, and from Corral Creek, Camas Co., Idaho, the Elizabethtown district, Colfax Co., New Mexico, and the Monarch tungsten mine, Inyo Co., California; Mundo Nuovo and Junin, Peru; the Quechisla district, Potosí, Bolivia; large crystals from Kirwa, Kigezi, Uganda; Gejui, Hunan, China; and the Tae wha mine, Chungju, South Korea. The sheet does not name Devon.
Ore and uses. The USGS 2021 Minerals Yearbook, Tungsten says wolframite is one of two principal minerals mined for tungsten. The USGS Mineral Commodity Summaries 2026, Tungsten says an estimated 60% of the tungsten consumed in the United States was used in cemented carbide parts for cutting and wear-resistant applications. This page names no ore grade or producer.
Dust. Questions about tungsten and manganese mineral dust go to toxic minerals in a collection; this page is not safety advice. More species are in the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.