It is highly toxic[citation needed] and a known carcinogen in humans.

Uncontrolled decomposition of nickel arsenide can give rise to further toxic nickel compounds.

The damage to the miners' lungs was documented by Georgius Agricola in the 16th century: "kupfer-nickel" ores in the Schneeberg mines contained red-colored NiAs mineral originally mistaken for the copper ore, thus the German: kupfer (copper) in the name.

The German: Nickel (demon) name was reflecting the damage it did to the health of the workers,[1] in addition to them being unable to extract any copper from this ore.

[2] The main compound within nickeline, nickel arsenide (NiAs), can be prepared by direct combination of the elements: Ni(s) + As(s) → NiAs(s)[3]