Is millerite magnetic?
Unrecorded. The millerite sheet prints no magnetic property and USGS Table 1 has no millerite row. Associates pentlandite and pyrrhotite are ferromagnetic.
Not on the record. The Handbook sheet for millerite, NiS, hardness 3 to 3.5, prints no magnetic property, and USGS Open-File Report 99-529 Table 1 has no millerite row. Of its 10 nickel rows, 3 are pulled on the separator. Two of millerite’s associates, pentlandite at 0.01 amp and pyrrhotite at 0.01 to 0.05, are ferromagnetic by USGS.
In short
- Two sources, no measurement. The Handbook of Mineralogy millerite sheet gives NiS, hexagonal, capillary crystals to 7 cm, hardness 3 to 3.5, density 5.5, and no magnetic property. A script parsing all 377 data rows of USGS Open-File Report 99-529, Table 1 finds no millerite row. This page therefore makes no claim about millerite on a magnet, in either direction.
- The nickel-row ledger. Matching every Table 1 row to the September 2026 IMA-CNMNC Master List by script, 10 rows have nickel in the formula. Three are pulled: pentlandite, best 0.01 amp, violarite 0.20 to 0.30, népouite 0.40 to 0.50. Seven stay behind above 1.70 amp: nickeline, breithauptite, gersdorffite, melonite, siegenite, nickelskutterudite and ullmannite. The two pulled sulfides are the two with iron in the formula.
- What pulls in a millerite specimen. Of the 15 associates on the millerite sheet, 13 have a Table 1 row. Five are pulled: pentlandite (best 0.01 amp), pyrrhotite (0.01 to 0.05), siderite (0.20 to 0.30), ankerite (0.40 to 0.50) and chalcopyrite (0.70 to 1.30). USGS names pyrrhotite and pentlandite among the ferromagnetic minerals, strongly attracted to a magnet, like a piece of iron.
- Documented failure: the silent sheet. The pentlandite sheet prints no magnetic property, yet USGS pulled its 2 samples at a best 0.01 amp and calls it ferromagnetic. The millerite sheet’s silence is the same kind of silence: absence from the source, not a measurement. The Marbridge analysis also carries 1.03 wt% iron, 1.7% of its metal atoms.
- The decision, in order. Neither source tests a hand magnet. If a brass-yellow piece pulls, suspect pyrrhotite or pentlandite first: the pyrrhotite sheet says magnetic, varying in intensity inversely with iron content. Then confirm the needles by habit and hardness, 3 to 3.5, as set out on millerite.
| Name (IMA) | Formula (IMA) | Iron in formula | Total range (amp) | Best range (amp) | Samples | Handbook magnetism | Reading |
|---|---|---|---|---|---|---|---|
| Pentlandite | (Ni,Fe)9S8 | Yes | Below 0.01 to 0.30 | 0.01 | 2 | None printed | Ferromagnetic (USGS names it) |
| Violarite | FeNi2S4 | Yes | 0.01 to 0.80 | 0.20 to 0.30 | 1 | None printed | Pulled |
| Népouite [Nepouite] | Ni3Si2O5(OH)4 | No | 0.20 to 0.70 | 0.40 to 0.50 | 1 | No sheet used | Pulled, a nickel silicate |
| Nickeline [Niccolite] | NiAs | No | Above 1.70 | Above 1.70 | 6 | None printed | Stays behind |
| Breithauptite | NiSb | No | Above 1.70 | Above 1.70 | 2 | No sheet used | Stays behind |
| Gersdorffite | NiAsS | No | Above 1.70 | Above 1.70 | 1 | None printed | Stays behind |
| Melonite | NiTe2 | No | Above 1.70 | Above 1.70 | 1 | No sheet used | Stays behind |
| Siegenite | CoNi2S4 | No | Above 1.70 | Above 1.70 | 1 | No sheet used | Stays behind |
| Nickelskutterudite [Skutterudite-(Ni)] | NiAs3 | No | 0.50 to above 1.70 | Above 1.70 | 1 | No sheet used | Stays behind |
| Ullmannite | NiSbS | No | Above 1.70 | Above 1.70 | 1 | No sheet used | Stays behind |
| Millerite | NiS | No | No row | No row | 0 | None printed | Not measured |
| Pyrrhotite (associate) | Fe7S8 | Yes | Below 0.01 to 0.70 | 0.01 to 0.05 | 7 | Magnetic, varying inversely with iron content | Ferromagnetic (USGS names it) |
Is millerite magnetic? What the Handbook sheet says
The millerite sheet prints no magnetic property. The Handbook of Mineralogy millerite sheet gives NiS, hexagonal, as slender to capillary crystals to 7 cm in radiating hairlike groups, hardness 3 to 3.5, density 5.5, pale brass-yellow to bronze-yellow with a greenish black streak, and its physical-properties line stops at density. A case-insensitive search of the sheet text for magnet finds nothing. The species facts, with its nickel worked by mass, are on millerite.
Its neighbours, as printed. The pyrrhotite sheet says magnetic, varying in intensity inversely with iron content, and the magnetite sheet strongly magnetic. The pentlandite, violarite, polydymite, heazlewoodite, vaesite, godlevskite, nickeline, gersdorffite, chalcopyrite and marcasite sheets print no magnetic property; the pyrite sheet prints paramagnetic. The site-wide summary of which sheets record magnetism is on which minerals are magnetic and is not repeated here.
What this page does not claim. No source fetched for this page measures millerite’s magnetic response. USGS says, in general, that chemistry is the main factor controlling magnetic susceptibility, and that iron and copper are two elements responsible for paramagnetic susceptibility in some minerals. It does not mention nickel in that sentence, and this page does not extend it.
Did USGS measure millerite? No: the nickel-row ledger
Table 1 of the USGS report has no millerite row; it has 10 rows of other nickel minerals. USGS Open-File Report 99-529 (Rosenblum and Brownfield) ran 1084 samples of 378 mineral species through Frantz isodynamic separators, on grains of 125 to 150 micrometres at a 15° side tilt. Method: a script parsed every data line of Table 1 (377 rows), matched each name to its row on the September 2026 IMA list (exact name, with aliases for the old names niccolite, skutterudite-(Ni) and nepouite), and kept rows whose IMA formula contains nickel. No row is named millerite.
The ledger. Three of the 10 are pulled. Pentlandite, (Ni,Fe)9S8, total range below 0.01 to 0.30 amp, best 0.01, across 2 samples; violarite, FeNi2S4, 0.01 to 0.80, best 0.20 to 0.30, 1 sample; népouite, Ni3Si2O5(OH)4, a nickel silicate, 0.20 to 0.70, best 0.40 to 0.50, 1 sample. Seven stay behind with a best range above 1.70 amp, the separator’s maximum: nickeline (6 samples, as niccolite), breithauptite (2), gersdorffite, melonite, siegenite, nickelskutterudite and ullmannite (1 each). The two pulled sulfides are the two with iron in the IMA formula; the seven without iron stayed behind; népouite, with no iron, was pulled.
Why the ledger is not a prediction. Millerite, NiS, has no iron in its IMA formula and is oxygen-free, like the seven that stayed behind; but it is not one of them, and ten rows of other species do not measure an eleventh. The ledger says what USGS measured on nickel minerals, and stops. The titanium, iron-oxide and spinel versions of this kind of reading are on is ilmenite magnetic, is hematite magnetic and is chromite magnetic, and the arsenic rows on is arsenopyrite magnetic; none of their assets is repeated here.
What makes a millerite specimen pull a magnet? The associate check
Two of millerite’s listed associates are ferromagnetic by the USGS definitions. The millerite sheet’s association line names 15 minerals. Thirteen have a Table 1 row (polydymite and cubanite do not). Five are pulled: pentlandite, best 0.01 amp; pyrrhotite, total below 0.01 to 0.70, best 0.01 to 0.05, 7 samples; siderite, best 0.20 to 0.30 across 17 samples; ankerite, 0.40 to 0.50; chalcopyrite, 0.70 to 1.30, marked depends on chemistry. Eight stay behind above 1.70: gersdorffite, nickeline, galena, sphalerite, pyrite, calcite, dolomite and barite.
The definitions. USGS calls ferromagnetic the minerals strongly attracted to a magnet, like a piece of iron, and names magnetite, maghemite, pyrrhotite and pentlandite among them; paramagnetic minerals are less magnetic and separable at up to 1.70 amps; diamagnetic minerals are nonmagnetic at 1.70 amps. It warns that when micro-inclusions of magnetite or other ferromagnetic minerals are present, the lower limit of extraction is difficult or impossible to determine.
Documented failure: the silent sheet. The pentlandite sheet prints no magnetic property; USGS pulled pentlandite at 0.01 amp and names it ferromagnetic. A Handbook sheet that says nothing about magnetism is not saying a mineral is non-magnetic. The same caution applies to millerite’s sheet, and to the Marbridge analysis on it, which carries 1.03 wt% iron, 1.7% of the metal atoms.
How to read a magnet on a millerite specimen
A pull from a brass-yellow piece points first at pyrrhotite or pentlandite, not at millerite. Neither source tests a hand magnet, so this is a reading of the two records, not a test result. Pyrrhotite is bronze-yellow to pinchbeck-brown, hardness 3.5 to 4.5, tabular or massive; pentlandite pale bronze-yellow, 3.5 to 4, massive and granular; millerite pale brass-yellow, 3 to 3.5, in capillary needles. The habit is the quickest separation. Pyrrhotite has its own page, and whether a tetrahedrite or wolframite specimen pulls is on is tetrahedrite magnetic and is wolframite magnetic.
Before the magnet. Weight, where the piece is solid: a 20.00 g piece reads 16.36 g in water as millerite, 15.63 to 15.70 g as pyrrhotite and 15.65 to 16.00 g as pentlandite. A spray of needles cannot be weighed that way; hardness on a crystal tip and the habit are what is left. The methods are on how to measure specific gravity at home and how to test mineral hardness properly. magnetite has its own page.
Who each label is wrong for. Write millerite on the label when the needles, the colour and the hardness agree, whatever the magnet does. Write a magnetic associate, tentatively, when one grain or band pulls. The magnetism questions are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.