Is tetrahedrite magnetic
The three tetrahedrite-group Handbook sheets record no magnetism. 5 of 176 sheets record any. If your specimen pulls a magnet, here is what to test next.
Is tetrahedrite magnetic? Not on the record. The Handbook sheets for tetrahedrite, tennantite and freibergite say nothing about magnetism, while 5 of the 176 sheets in this site's reference set do. So a tetrahedrite specimen, hardness 3 to 4.5, density 4.97, that pulls a magnet is telling you about a second mineral in it, or that it is not tetrahedrite.
In short
- No response is the normal result and needs no fixing. The Handbook sheets for tetrahedrite, tennantite and freibergite record no magnetic property of any kind. Searching all 176 sheets in this site's reference set, 5 record one: magnetite strongly magnetic, pyrrhotite magnetic, greenalite moderately magnetic, pyrite paramagnetic, borax diamagnetic.
- A strong pull on one grain is a second mineral. In this set the candidates that pull are magnetite and pyrrhotite. Neither is on tetrahedrite's association list, and neither sheet mentions tetrahedrite. They share associates with it, chalcopyrite and pyrite, which is a reason to test rather than a reason to assume.
- A strong pull on the whole piece suggests it is not tetrahedrite. Magnetite is the black metallic look-alike: density 5.175 against tetrahedrite's 4.97 is too close to help, but hardness 5.5 to 6.5 against 3 to 4.5 and octahedra against tetrahedra settle it.
- Of tetrahedrite's 12 listed associates, 1 has a magnetic entry: pyrite, paramagnetic. That is a weak effect, not the snap of a magnet onto magnetite. A faint drag felt only with a strong rare-earth magnet is not something any of these sheets predicts or explains.
- Tetrahedrite has not been a species name since 2019. The September 2026 IMA list holds tetrahedrite-(Fe), -(Zn) and others, and a magnet will not tell them apart. The label that survives a magnet test reads tetrahedrite group.
| What you see | Likely cause | Test that separates it | What to do |
|---|---|---|---|
| No response, even with a rare-earth magnet | Normal. No magnetic property is recorded on any of the 3 group sheets | None needed | Nothing. Record the test on the catalogue card |
| Faint drag with a strong rare-earth magnet only | Not recorded on any group sheet. Pyrite, a listed associate, is recorded only as paramagnetic | Repeat on a clean, single-crystal area away from other minerals | Do not treat it as identifying anything |
| Strong pull at one spot or grain | A second, magnetic phase: in this set, magnetite or pyrrhotite | Colour and hardness of that grain: black and 5.5 to 6.5 suggests magnetite; bronze and 3.5 to 4.5 suggests pyrrhotite | Note the associate on the label as tentative until tested |
| Pull only along a saw cut, drill hole or chisel mark | Steel left on the surface by tools | Does the response move with the mark rather than with a mineral grain? | Clean it mechanically, then retest |
| Strong pull on the whole piece | Probably not tetrahedrite. Magnetite is the metallic black look-alike | Hardness 5.5 to 6.5 against 3 to 4.5; octahedra against tetrahedra; density 5.175 against 4.97 is too close | Re-identify the specimen before relabelling it |
Is tetrahedrite magnetic? What the sheets record, and how we checked
The Handbook of Mineralogy records no magnetic property for any of the three tetrahedrite-group sheets. Method: every one of the 176 Handbook of Mineralogy sheets in this site's reference set was converted with pdftotext -layout and searched for the string magnet. The string occurs on 21 sheets, mostly as the mineral magnetite in association lists or the place-name Magnet Cove. Restricting to the Physical Properties field leaves 5 sheets: magnetite, Strongly magnetic; pyrrhotite, Magnetic, varying in intensity inversely with iron content; greenalite, Moderately magnetic; pyrite, Paramagnetic; a semiconductor; and borax, diamagnetic.
Tetrahedrite, tennantite and freibergite are not among them. Their physical-properties blocks record hardness (3 to 4.5 for tetrahedrite and tennantite, not determined for freibergite), Vickers hardness and density, plus fracture and tenacity for the first two, and stop. A reference that records pyrite's paramagnetism and borax's diamagnetism would have room for tetrahedrite's; it has none. We state that as absence from the source, not as a measurement of our own.
Tetrahedrite's association field lists 12 minerals: chalcopyrite, galena, sphalerite, pyrite, bornite, acanthite, calcite, dolomite, siderite, barite, fluorite and quartz. All 12 have sheets in the set, and only pyrite's records any magnetic property, as paramagnetic. Neither magnetite's nor pyrrhotite's sheet names tetrahedrite or tennantite anywhere. Background on the species and its name is on the tetrahedrite species page.
My tetrahedrite is magnetic: the tests, ordered by how often each is the answer
A magnet response on a tetrahedrite specimen is information about something other than the tetrahedrite. The order in the table is our judgement of likelihood, not a count; nobody publishes one. Work down it.
Localise first. Hang a small magnet on a thread and move it slowly over the specimen. A pull that follows one grain, one seam or one band is a second phase; a pull that is the same everywhere is the whole piece. This costs nothing and separates the table's last three rows at once.
Then test the grain, not the specimen. The two candidates in the set that pull a magnet differ from each other clearly. Magnetite: black, streak black, hardness 5.5 to 6.5, typically octahedral. Pyrrhotite: bronze-yellow to pinchbeck-brown and quick to tarnish, streak dark greyish black, hardness 3.5 to 4.5, commonly massive. Tetrahedrite itself: flint-grey to iron-black, streak black to brown, hardness 3 to 4.5, tetrahedral. So a steel point, at about 5.5, marks tetrahedrite and pyrrhotite and struggles on magnetite; colour then separates the two soft ones. Methods on how to use a streak plate and how to test mineral hardness properly.
Why pyrrhotite is worth checking even though tetrahedrite's sheet does not list it: pyrrhotite's association field lists pyrite, chalcopyrite and many other sulfides, and magnetite's hydrothermal associates include pyrrhotite, pyrite, chalcopyrite and sphalerite. That shared company is the reason to test, and not evidence either mineral is present in your piece. Pyrrhotite has its own page at pyrrhotite.
Why the whole specimen pulling is the one to take seriously
If the whole piece snaps to a magnet, the label is probably wrong. Tetrahedrite and magnetite are both black, metallic and heavy. Density 4.97 against 5.175 is a 4.1% difference, which is too narrow to rely on at home against a specimen with any matrix. What separates them in the hand is hardness, 3 to 4.5 against 5.5 to 6.5, and form: the tetrahedrite sheet records tetrahedral crystals to 15 cm and the magnetite sheet typically octahedral. A magnetite octahedron resting on one face can look like a tetrahedron from above, so count the faces.
The other whole-specimen case is massive pyrrhotite mislabelled from an old mine sample. Its bronze colour usually gives it away on a fresh surface, and a massive piece of tetrahedrite-group ore can carry pyrrhotite through it without either being wrong on the label. Similar-looking metallic species are compared on the bournonite and chalcopyrite pages.
The fix is an honest label, not a stronger magnet. Keep the original label, add a card reading tetrahedrite group, with a magnetic phase, possibly magnetite or whatever your tests supported, and date it, as set out on how to label and catalogue a mineral collection. The rest of this section is indexed at the collecting guides. Nothing here is offered for sale; the wanted list is the only commercial route.