Nickeline
Nickeline, NiAs, is pale copper-red: hexagonal, hardness 5 to 5.5, density 7.784, streak pale brownish black. It is 43.93% nickel; niccolite is the older name.
Nickeline is nickel arsenide, NiAs on the IMA list (A, 1967 s.p.): hexagonal, pale copper-red tarnishing gray to blackish, hardness 5 to 5.5, density 7.784, streak pale brownish black. Ideal NiAs is 43.93% nickel and 56.07% arsenic. A 20.00 g piece reads 17.43 g in water; native copper, hardness 2.5 to 3, reads 17.77 g.
In short
- The species. The Handbook of Mineralogy sheet gives NiAs, hexagonal, usually granular, reniform or arborescent, rarely in striated crystals to 1.5 cm twinned on {10-11} as fourlings; hardness 5 to 5.5, density 7.784, pale copper-red tarnishing gray to blackish, streak pale brownish black. The September 2026 IMA-CNMNC Master List gives NiAs, status A, 1967 s.p., country unknown; the sheet marks no type locality.
- The kupfernickel check. The name records a copper look-alike that yielded no copper. Hardness parts them: nickeline 5 to 5.5, native copper 2.5 to 3 and highly malleable, bornite 3 to 3.25. Weight backs it up for bornite: a 20.00 g piece reads 17.43 g in water as nickeline and 16.05 to 16.06 g as bornite, 1.37 g apart. Copper, 17.77 g, is only 0.33 g heavier.
- Documented failure: the other copper-red arsenide and antimonide. Breithauptite, NiSb, also pale copper-red and in the same Handbook group, reads 17.37 to 17.57 g; maucherite, Ni11As8, 17.50 g. Both are within 0.14 g of nickeline, and both are hardness 5 to 5.5. The streak does it: breithauptite reddish brown, maucherite blackish gray, nickeline pale brownish black.
- Worked on the sheet: Jáchymov. The sheet’s Jáchymov, Czech Republic, microprobe analysis has 43.2 wt% Ni, 0.4 Co, 0.2 Fe, 55.9 As, 0.1 Sb and 0.1 S. Converted to atoms, metals stand at 0.995 to the arsenic-site atoms, nickel holds 98.6% of the metals, arsenic 99.5% of its site: the sheet’s (Ni0.98Co0.01Fe0.01)As1.00. Its nickel is 98.3% of the ideal 43.93.
- Niccolite, magnet and arsenic. USGS ran 6 samples under the old name niccolite; all stayed behind above 1.70 amp, and the report calls niccolite nonmagnetic. The IMA list has 0 lines containing niccolite. Nickeline is 56.07% arsenic by mass; for handling, see toxic minerals in a collection, which is not advice.
| Name | Formula (IMA), status | System (sheet) | Hardness | Density | 20.00 g piece in water | Streak (sheet) | Colour (sheet) | Separates nickeline? |
|---|---|---|---|---|---|---|---|---|
| Nickeline | NiAs; A, 1967 s.p. | Hexagonal | 5–5.5 | 7.784 | 17.43 g | Pale brownish black | Pale copper-red, tarnishes gray to blackish | The species |
| Native copper | Cu; G | Cubic | 2.5–3 | 8.95 | 17.77 g | n.p. | Pale rose, quickly darkens to copper-red | By hardness; highly malleable and ductile |
| Bornite | Cu5FeS4; A, 1962 s.p. | Orthorhombic, pseudocubic | 3–3.25 | 5.06–5.08 | 16.05–16.06 g | Pale grayish black | Copper-red to pinchbeck-brown, tarnishes iridescent purplish | By hardness and weight (1.37 g) |
| Breithauptite | NiSb; G, 1845 | Hexagonal | 5.5 | 7.591–8.23 | 17.37–17.57 g | Reddish brown | Pale copper-red, may be with violet tint | Not by weight or hardness; by streak |
| Maucherite | Ni11As8; G, 1913 | Tetragonal | 5 | 8.00 | 17.50 g | Blackish gray | Platinum-gray with reddish tint, tarnishes coppery red | Not by weight (0.07 g); by colour and streak |
| Pyrrhotite | Fe7S8; G, 1835 | Monoclinic, pseudohexagonal | 3.5–4.5 | 4.58–4.65 | 15.63–15.70 g | Dark grayish black | Bronze-yellow to pinchbeck-brown | By weight; its sheet says magnetic |
| Annabergite | Ni3(AsO4)2(H2O)8; G, 1852 | Monoclinic | 1.5–2.5 | 3.07 | 13.49 g | Pale green to white | Apple-green, pale green, pale rose, white, gray | The green alteration crust, not a look-alike |
What is nickeline? Nickel arsenide, pale copper-red
Nickeline is NiAs, a pale copper-red hexagonal nickel arsenide that is seldom in crystals. The Handbook of Mineralogy nickeline sheet gives point group 6/m 2/m 2/m, space group P63/mmc, commonly in granular aggregates, reniform masses with radial structure, and reticulated and arborescent growths; rarely as distorted, horizontally striated crystals terminated by {10-11}, to 1.5 cm. It twins on {10-11}, producing fourlings, and possibly on {31-41}. Fracture conchoidal, brittle, hardness 5 to 5.5, measured density 7.784 against a calculated 7.834. The sheet prints no cleavage.
Colour and optics. Pale copper-red, tarnishing gray to blackish; white with a strong yellowish pink hue in reflected light; streak pale brownish black; lustre metallic. Pleochroism strong, anisotropism very strong, pale greenish yellow to slate-gray in air. The sheet places it in the nickeline group; the breithauptite sheet puts NiSb in the same group. The IMA list has no group column and 0 lines containing nickeline group.
What the IMA list records. The September 2026 list gives nickeline NiAs with status A and 1967 s.p., an approval by special procedure, and unknown in the country column; the sheet marks no type locality either. A field scan and a token scan of the list each find exactly 1 row written NiAs. Nickeline is the IMA name; niccolite, which Minerals.net says is still used for the same mineral and which the USGS table below uses, has no row.
Nickeline or native copper? The kupfernickel check
Hardness separates nickeline from the copper-red minerals it was once taken for; the streak separates it from its own relatives. The sheet derives the name from the German kupfernickel, or Devil’s copper, as the mineral was believed to contain copper but yielded none. Native copper, on its Handbook sheet, is hardness 2.5 to 3 and highly malleable and ductile; bornite is 3 to 3.25 and tarnishes iridescent purplish; nickeline is 5 to 5.5 and brittle. The method is on how to test mineral hardness properly.
Weight, where the piece is solid. At the sheets’ measured densities a 20.00 g piece reads 17.43 g in water as nickeline, 17.77 g as copper, 16.05 to 16.06 g as bornite and 15.63 to 15.70 g as pyrrhotite. Bornite is 1.37 g away and pyrrhotite further; copper only 0.33 g. The method is on how to measure specific gravity at home.
Documented failure: breithauptite and maucherite. Breithauptite, NiSb, is pale copper-red, sometimes with a violet tint, hardness 5.5, density 7.591 to 8.23, and reads 17.37 to 17.57 g, straddling nickeline’s 17.43 g. Maucherite, Ni11As8, hardness 5, density 8.00, reads 17.50 g, 0.07 g away, and the maucherite sheet lists nickeline among its associates. Neither weight nor hardness parts the three. The streak does: breithauptite reddish brown, maucherite blackish gray, nickeline pale brownish black. The method is on how to use a streak plate.
How much nickel and arsenic is in nickeline?
Ideal NiAs is 43.93% nickel and 56.07% arsenic by mass. Worked on standard atomic weights (Ni 58.693, As 74.922), and printed identically in the sheet’s ideal column. For comparison on the same weights: breithauptite, NiSb, is 32.53% nickel, and maucherite, Ni11As8, 51.86%.
Worked on the sheet’s analysis. The Jáchymov, Czech Republic, electron-microprobe analysis has 43.2 wt% Ni, 0.4 Co, 0.2 Fe, 55.9 As, 0.1 Sb and 0.1 S, total 99.9. Divided by atomic weights, the metals stand at 0.995 to the arsenic, antimony and sulfur together; nickel holds 98.6% of the metal atoms, and arsenic 99.5% of its site. That is the sheet’s (Ni0.98Co0.01Fe0.01)Σ=1.00As1.00. The nickel is 98.3% of the ideal 43.93.
What this page does not claim. The sheet’s occurrence line calls nickeline a minor component of Ni–Cu ores in high-temperature hydrothermal veins, also massive and in disseminations in peridotite and norite. No USGS or BGS source fetched for this page names nickeline as a nickel ore, so this page makes no ore claim. Arsenic is 56.07% of the ideal formula; what that means for handling is not covered here. See toxic minerals in a collection; nothing on this page is health or safety advice.
Is nickeline magnetic, and what is the green coating?
Nickeline is nonmagnetic on the USGS record. USGS Open-File Report 99-529 (Rosenblum and Brownfield) ran 6 samples under the name niccolite through a Frantz isodynamic separator; all had a total and best range above 1.70 amp, the separator’s maximum. Its text says niccolite, cobaltite and skutterudite are nonmagnetic. The nickeline sheet prints no magnetic property. The nickel rows of that table are set out on is millerite magnetic and are not repeated here.
The green crust. The Handbook annabergite sheet gives Ni3(AsO4)2·8H2O, apple-green to pale green, hardness 1.5 to 2.5, as an uncommon secondary mineral formed by the alteration of Co–Ni-bearing arsenides and sulfides, in the oxidized zone of hydrothermal deposits. Its associates include nickeline and maucherite, and it forms a series with erythrite. A soft green film on a copper-red arsenide is consistent with that sheet; the sheets do not say every green film is annabergite.
Where nickeline is found. The Distribution field names Eisleben and Mansfeld, Saxony-Anhalt; St. Andreasberg, Harz Mountains; Schneeberg, Saxony; crystallized at Richelsdorf, Hesse-Nassau; Schladming, Austria; Jáchymov (Joachimsthal), Czech Republic; the Chalanches mine near Allemont, France; Silver Cliff and the Gem mine, Colorado; the Cobalt–Gowganda and Sudbury districts and Silver Islet, Ontario; Cochabamba, Bolivia; the Aït Ahmane mine, 10 km east of Bou Azzer, Morocco; the Talmessi mine near Anarak, Iran; and the Ban Phuc Ni–Cu deposit, Vietnam. Its associates include skutterudite–nickel-skutterudite, safflorite, rammelsbergite, gersdorffite, maucherite, breithauptite, bismuth and bismuthinite. The nickel sulfide is millerite; the platinum diarsenide is sperrylite. The rest is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.