Nickeline (a.k.a. niccoline, niccolite) is a nickel arsenide mineral - NiAs.  It has a metallic luster, a metallic pinkish-orange to pale copper color that tarnishes gray, and a gray streak.  Nickeline is fairly heavy for its size, is moderately hard (H=5 to 5.5), and has no cleavage.  It tends to occur with some Ni-Fe-Cu sulfide/arsenide minerals and with some Co-Ag minerals.


Nickeline (field of view ~1.7 cm across)



Photo gallery of nickeline



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