nickeline

{{Infobox mineral | name = Nickeline | category = Arsenide mineral | boxwidth = | image = Nickeline.jpg | imagesize = 260px | caption = | formula = Nickel arsenide (NiAs) | IMAsymbol = Nc | strunz = 2.CC.05 | system = Hexagonal | class = Dihexagonal dipyramidal (6/mmm) H-M symbol: (6/m 2/m 2/m) | symmetry = P63/mmc | unit cell = a = 3.602 Å, c = 5.009 Å; Z = 2 | color = Pale copper red with blackish tarnish. White with strong yellowish pink hue on polished section strongly anisotropic | habit = Massive columnar to reniform, rarely as distorted, horizontally striated, {1011} terminated crystals | twinning = On {1011} producing fourlings | cleavage = {1010} Imperfect, {0001} Imperfect | fracture = Conchoidal | tenacity = Brittle | mohs = 5 – 5.5 | luster = Metallic | diaphaneity = Opaque | refractive = | pleochroism = Strong (reflected light) | streak = Brownish black | gravity = 7.8 | melt = | fusibility = 2 | solubility = | other = Garlic odor on heating | references = }} Nickeline or niccolite is the mineral form of nickel arsenide. The naturally occurring mineral contains roughly 43.9% nickel and 56.1% arsenic by mass, but composition of the mineral may vary slightly.

Small quantities of sulfur, iron and cobalt are usually present, and sometimes the arsenic is largely replaced by antimony. This last forms an isomorphous series with breithauptite (nickel antimonide).