Is stibnite magnetic
No. Stibnite's sheet records no magnetism, and USGS left 6 of 6 samples of this antimony sulphide unpulled at 1.70 amp. Of 4 look-alikes, only jamesonite was.
Is stibnite magnetic? No. The Handbook sheet for stibnite, Sb2S3, hardness 2, density 4.63, records no magnetic property, and USGS Open-File Report 99-529 left all 6 stibnite samples unpulled at 1.70 amp, its separator maximum: diamagnetic by that report's definition. Of four grey needle look-alikes, USGS pulled only jamesonite, which contains iron.
In short
- Stibnite is not magnetic on either record. The Handbook of Mineralogy sheet gives Sb2S3, lead-gray, highly flexible, hardness 2 and density 4.63, and prints no magnetic property. USGS passed stibnite grains, 125 to 150 µm, through a laboratory separator, and all 6 samples stayed behind at 1.70 amp, the separator's highest current.
- What not magnetic means here. USGS defines diamagnetic as nonmagnetic at 1.70 amp and repelled by stronger electromagnets, and reserves strongly attracted to a magnet for ferromagnetic minerals such as magnetite. Stibnite falls in the first class. Neither source tests a hand magnet.
- The iron-needle check: among the grey needles people take for stibnite, suspect the ones with iron in the formula. Of the five sheets compared here, jamesonite and berthierite carry iron. USGS pulled jamesonite at 0.90 to 1.00 amp, from a single sample, and never tabled berthierite; stibnite, bismuthinite and boulangerite all stayed behind.
- The scale will not separate stibnite from berthierite. A 20.00 g piece reads 15.68 g in water as stibnite and 15.69 g as berthierite. Tenacity and streak do it: stibnite is highly flexible with a lead-gray streak; berthierite is brittle with a dark brownish gray streak.
- A pull on a stibnite specimen comes from something else. USGS notes that micro-inclusions of magnetite make a lower extraction limit hard to determine. Whether stibnite is toxic is a different question, routed to the toxic-minerals page. This is not health, safety or legal advice.
| Mineral | Formula (Handbook) | Iron by mass | USGS best range (amp) | Samples | Class, by USGS definitions | Hardness; tenacity | Streak | 20.00 g in water |
|---|---|---|---|---|---|---|---|---|
| Stibnite | Sb2S3 | 0% | Above 1.70 | 6 | Diamagnetic | 2; highly flexible, not elastic | Lead-gray | 15.68 g |
| Bismuthinite | Bi2S3 | 0% | Above 1.70 | 2 | Diamagnetic | 2–2.5; flexible, somewhat sectile | Lead-gray | 17.05 g |
| Boulangerite | Pb5Sb4S11 | 0% | Above 1.70 | 5 | Diamagnetic | 2.5–3; brittle, flexible in thin crystals | Brownish | 16.77 g |
| Jamesonite | Pb4FeSb6S14 | 2.71% | 0.90–1.00 (total 0.60–1.30) | 1 | Paramagnetic | 2.5; brittle | Not printed on the sheet | 16.45 g |
| Berthierite | FeSb2S4 | 13.06% | Not in the USGS table | - | Not measured: no prediction | 2–3; brittle | Dark brownish gray | 15.69 g |
| Magnetite, for scale | Fe2+Fe3+2O4 (IMA list) | 72.36% | 0.01 (total below 0.01 to 0.05) | 6 | Ferromagnetic; sheet: strongly magnetic | - | - | - |
Is stibnite magnetic? What the Handbook sheet records
The Handbook of Mineralogy sheet for stibnite records no magnetic property. It gives Sb2S3, orthorhombic, in slender to stout crystals to 0.65 m, bent crystals not uncommon. Cleavage is perfect and easy on {010}, hardness 2, measured density 4.63. Colour lead-gray, tarnishing blackish or iridescent; streak lead-gray; lustre metallic, splendent on cleavage surfaces; tenacity highly flexible but not elastic, slightly sectile. It forms a series with bismuthinite and is dimorphous with metastibnite.
Silence on a sheet is not a measurement. The sheet's chemistry gives 71.69% antimony and 28.31% sulphur for ideal Sb2S3 and contains no iron. An absent entry tells you only that the source did not record magnetism, so the question goes to a laboratory measurement. The species itself, including its flexibility, is on stibnite.
Stibnite is antimony sulphide, not antimony metal. The IMA list gives Sb2S3, grandfathered, 1832, country of first description unknown. The sheet calls it the most important ore of antimony, although large deposits are rare.
What USGS measured: 6 of 6 stibnite samples stayed behind
USGS measured stibnite on a separator, and it was not pulled at the highest current the machines reached. USGS Open-File Report 99-529, Magnetic Susceptibilities of Minerals (Rosenblum and Brownfield) fed dry grains, 125 to 150 µm, through Frantz isodynamic separators at a 15 degree side tilt and recorded the current at which each mineral was extracted. For stibnite, 6 samples, both the total range and the best range read above 1.70 amp.
The report's definitions, as written. Ferromagnetic minerals are strongly attracted to a magnet, like a piece of iron. Paramagnetic minerals are less magnetic and separable at up to 1.70 amp, the greatest value reached on a Frantz separator. Diamagnetic minerals are nonmagnetic at 1.70 amp and would be repelled by electromagnets with stronger currents. Stibnite is diamagnetic on those definitions. The report does not give susceptibilities in cgs units, so this is a class, not a number.
Dark does not mean magnetic. USGS writes that dark-coloured and opaque minerals are generally extracted below 1.00 amp, and names many sulfides among the exceptions. The same framing for galena is on is galena magnetic; the minerals whose sheets do record magnetism are on which minerals are magnetic.
The iron-needle check: which grey needle gets pulled
The iron-needle check: of the grey needles taken for stibnite, the ones to suspect of responding to a magnetic separator are those with iron in the formula. Five sheets are compared in the table: stibnite, bismuthinite, boulangerite, jamesonite and berthierite. Calculated on standard atomic weights, two carry iron: jamesonite, Pb4FeSb6S14, 2.71%, and berthierite, FeSb2S4, 13.06%.
What USGS found among them. Stibnite (6 samples), bismuthinite (2) and boulangerite (5) all read above 1.70 amp. Jamesonite was pulled, best range 0.90 to 1.00 amp, but from one sample, and the report itself says that the greater the number of samples, the better the reliability. Berthierite has no row, so this page predicts nothing for it. USGS names iron and copper as two elements responsible for paramagnetic susceptibility in some minerals; the jamesonite result is consistent with that, and we claim no more.
Other checks do the work at home. Stibnite is highly flexible; jamesonite, berthierite and boulangerite are recorded as brittle, boulangerite flexible only in thin crystals. Berthierite's streak is dark brownish gray and boulangerite's brownish, against stibnite's lead-gray. Bismuthinite is the heavy one: 17.05 g in water for 20.00 g, against stibnite's 15.68 g. A sulfosalt cousin, bournonite, is separated on the stibnite page.
When the answer changes: a stibnite that pulls a magnet
If something on a stibnite specimen responds to a magnet, the response belongs to another mineral, to steel from a tool, or to a misidentified needle. USGS reserves strong attraction for ferromagnetic minerals such as magnetite, and notes that micro-inclusions of magnetite or other ferromagnetic minerals make the lower limit of extraction hard to determine. Neither source tests a hand magnet, so we make no prediction about one.
The berthierite case is the one to remember. Berthierite is dark steel-gray, often with an iridescent or pinchbeck-brown tarnish; the Handbook of Mineralogy sheet for berthierite lists stibnite as its first associate. On the sheets, the two weigh the same in water to within 0.01 g on a 20.00 g piece, so the scale will not separate them. A grey needle that is brittle and streaks brownish is not behaving as stibnite, whatever the magnet does. Related checks for a grey sulphide are on is tetrahedrite magnetic.
Toxicity is a separate question. It is not answered here; the general page is toxic minerals in a collection, with HSE EH40 and COSHH 2002 for workplace rules. This is not health, safety or legal advice. The identification pages are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.