Ferberite vs wolframite
Ferberite vs wolframite: ferberite is an IMA species, Fe2+(WO4); wolframite names the ferberite–hübnerite series. The iron-manganese line, and the FeO rule.
Ferberite is a species and wolframite is not. The IMA list has ferberite, Fe2+(WO4), and hübnerite, Mn2+(WO4), and no wolframite row; wolframite names their series. A piece is ferberite when iron atoms outnumber manganese: in an oxide analysis, FeO above 1.0128 times MnO. Hardness, 4 to 4.5 on both, cannot decide; streak and a density of 7.58 only point.
In short
- The verdict. Use “ferberite” for a piece analysed as iron-dominant, “hübnerite” for manganese-dominant, and “wolframite” for one that has not been analysed. The September 2026 IMA-CNMNC Master List has rows for ferberite, Fe2+(WO4), G, 1863, and hübnerite, Mn2+(WO4), G, 1865, and 0 lines containing “wolfram”; each Handbook sheet says it forms a series with the other.
- The FeO rule. Hatert and Burke (2008) give a two-atom series two names, each from its end member “to the 50 mol.% mark”. Analyses are printed as oxide weights, and FeO (71.844) is heavier than MnO (70.937), so the line falls at FeO = 1.0128 × MnO, not at equal weights. The 50:50 composition is WO3 76.46, FeO 11.85, MnO 11.70; an analysis with FeO and MnO both 11.78 is 49.68% iron, hübnerite.
- The sheets’ two analyses. Worked by atoms, the ferberite sheet’s Kurasawa, Japan, analysis (FeO 24.37, MnO 0.19) is 99.2% iron, and the hübnerite sheet’s Uncompahgre district, Colorado, analysis (FeO 0.24, MnO 23.40) is 1.0%. Both sit near the ends; neither sheet prints an intermediate analysis.
- What separates the ends. Streak: brownish black to black on ferberite, yellow to reddish brown or greenish grey on hübnerite. Transparency: nearly to entirely opaque against transparent to translucent. Density 7.58 against 7.12 to 7.18, so a 20.00 g piece reads 17.36 g in water against 17.19 to 17.21 g. Hardness (4 to 4.5), the {010} cleavage and the space group are the same on both.
- Documented failure: the middle of the series. The ferberite sheet says material approaching end-member composition is uncommon, and the streak, opacity and density above are printed for near-end-member material. The magnet does not rescue it: the ferberite sheet says slightly magnetic and the hübnerite sheet nothing, yet USGS Open-File Report 99-529, Table 1 pulled both, as set out on is wolframite magnetic.
| Composition | FeO, wt% | MnO, wt% | FeO ÷ MnO (line at 1.0128) | Iron, % of Fe + Mn (atoms) | Name it |
|---|---|---|---|---|---|
| Ferberite, ideal FeWO4 (sheet column 2) | 23.66 | 0 | — | 100 | Ferberite |
| Kurasawa, Japan (ferberite sheet, analysis 1) | 24.37 | 0.19 | 128 | 99.2 | Ferberite |
| Slightly iron-dominant (arithmetic) | 12.00 | 11.70 | 1.026 | 50.32 | Ferberite |
| The 50:50 composition, WO3 76.46 (arithmetic) | 11.85 | 11.70 | 1.0128 | 50.00 | The line |
| Equal oxide weights (arithmetic) | 11.78 | 11.78 | 1.000 | 49.68 | Hübnerite, narrowly |
| Uncompahgre district, Colorado (hübnerite sheet, analysis 1) | 0.24 | 23.40 | 0.010 | 1.0 | Hübnerite |
| Hübnerite, ideal MnWO4 (sheet column 2) | 0 | 23.43 | — | 0 | Hübnerite |
| Not analysed | — | — | — | Unknown | Wolframite (series name) |
Is wolframite a mineral or a series name?
A series name. A case-insensitive scan of the September 2026 IMA list finds 0 lines containing “wolfram”, the same result as on is wolframite magnetic. The list carries the two end members: ferberite, Fe2+(WO4), G, 1863, Spain, and hübnerite, Mn2+(WO4), G, 1865, USA. The ferberite sheet says it forms a series with hübnerite, and the hübnerite sheet says it forms a series with ferberite. Webmineral’s wolframite page calls wolframite the group name for the hübnerite–ferberite series, writes it (Fe,Mn)WO4, and gives its IMA status as not approved.
Where the word survives. In the ore literature: the USGS 2021 Minerals Yearbook, Tungsten says wolframite is one of two principal minerals mined for tungsten. There it names the ore mineral without splitting iron from manganese; it is not a species name for a crystal in a cabinet.
Where is the line between ferberite and hübnerite? The FeO rule
The rule. Hatert and Burke, Canadian Mineralogist 46, 717 (2008) set out the dominant-constituent rule, which Nickel had called the 50% rule: where only two kinds of atoms substitute, the series gets two names, “for each compositional range from the end members to the 50 mol.% mark”. The IMA formulas differ only in Fe2+ against Mn2+, so iron-dominant is ferberite and manganese-dominant is hübnerite.
Reading it off an oxide analysis. The sheets print analyses as weight per cent of oxides. FeO weighs 71.844 per mole and MnO 70.937, so equal weights are not equal atoms: the line sits where FeO is 1.0128 times MnO. Worked, the 50:50 composition Fe0.5Mn0.5WO4 is WO3 76.46, FeO 11.85 and MnO 11.70. An analysis showing FeO 11.78 and MnO 11.78 is 49.68% iron by atoms, so hübnerite; FeO 12.00 against MnO 11.70 is 50.32%, ferberite.
The two sheet analyses. Kurasawa ferberite, FeO 24.37 and MnO 0.19, is 99.2% iron; Uncompahgre hübnerite, FeO 0.24 and MnO 23.40, is 1.0%. They agree with is wolframite magnetic, which reports the same pair. Neither is anywhere near the line, so neither tests the rule; only an analysis of a genuinely intermediate crystal would.
Can you tell ferberite from hübnerite without an analysis?
Only at the ends. On the sheets, ferberite is black, dark brown in transmitted light, nearly to entirely opaque, with a brownish black to black streak; hübnerite is yellowish brown to reddish brown, blackish brown, black or rarely red, transparent to translucent, with deep blood-red internal reflections and a yellow to reddish brown or greenish grey streak. Measured density is 7.58 against 7.12 to 7.18: a 20.00 g piece reads 17.36 g in water against 17.19 to 17.21 g, 0.15 to 0.17 g apart, on the method at how to measure specific gravity at home.
What does not separate them. Hardness, 4 to 4.5 on both; the perfect {010} cleavage with partings on {100} and {102}, on both; monoclinic P2/c, on both. Topaz and fluorite are on both association lines. Seven areas, among them Cornwall, Colorado and Peru, are on both Distribution fields, at different mines, as counted on hübnerite.
Documented failure: the magnet and the middle. The ferberite sheet prints “Slightly magnetic” and the hübnerite sheet prints nothing, which looks like a test. It is not: USGS Open-File Report 99-529, Table 1 pulled 4 ferberite and 5 huebnerite samples in overlapping ranges, 0.20 to 0.50 and 0.20 to 0.60 amp, and the reasons are on is wolframite magnetic. And because the ferberite sheet says near-end-member material is uncommon, a crystal whose streak and density fall between the printed values is exactly the case the separators do not cover. The species pages, ferberite and hübnerite, carry each end member’s own data.
What should a ferberite or wolframite label say?
The decision rule. With an analysis: apply the FeO rule and write ferberite or hübnerite. Without one: write wolframite, which names the series and is not wrong. A label reading “wolframite (ferberite)” implies that an analysis was made. The Panasqueira page reads that mine’s material as ferberite on the sheet evidence and says the same thing: a single crystal needs an Fe/Mn analysis.
Related questions. Scheelite is the calcium tungstate, Ca(WO4), and is not in this series; its fluorescence is on is scheelite fluorescent. Questions about tungsten and manganese mineral dust go to toxic minerals in a collection; this page is not safety advice. More guides are in the collecting guides. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.