Niccolite (nickel arsenide) belongs to the nickeline group. Of these minerals, only it and (much more rarely) breithauptite occasionally find their way into jewelry as cut pieces.
The term “nickeline” is also used synonymously for the gemstone niccolite itself. In fact, the International Mineralogical Association (IMA) recommends the use of the name “nickeline” over “niccolite.” Nevertheless, the latter still enjoys frequent use.
You might also encounter the term “nickelite” used to refer to the gemstone. However, nowadays that name more commonly refers to a tin-based babbitt metal alloy, not the mineral NiAs.
Niccolite’s combination of colors and metallic luster make it very distinctive. Although this gem has a lower hardness (5-5.5) than other popular jewelry stones, it has no cleavage. It’s tough enough to be worn on pendants, bolo ties, and rings with protective settings.
Like other metallic gems, niccolites have a colored streak. They leave a pale, brownish black mark. Keep in mind that streak testing can destroy your specimen. Conduct this exam on a piece of rough, never a finished gem, only as a last resort.
Niccolite’s unusual pale, peachy, copper-red color and very high specific gravity (7.78) will usually readily distinguish it from most other gemstones. However, these properties as well as its hardness overlap with those of its group mate breithauptite. Breithauptites tend to have a violet tint to their reddish copper color. Their streak is also reddish brown.
Lapidaries could cut cabochons of any size desired from massive pieces.
Niccolites may tarnish to darker colors, such as gray or black. If exposed to moist air, niccolites may form a green nickel coating known as annabergite. A coat of clear nail polish may prevent this.
Keep any niccolite jewelry or gemstones stored dry to avoid tarnish and separated from harder stones to avoid contact scratches. Niccolites are tough, but avoid rough handling. Wear them as occasional gems. Consult our gemstone jewelry cleaning guide for care recommendations.
Please note that niccolite contains both nickel and arsenic. When cutting this material, avoid ingesting or inhaling particles, protect your eyes, and wash your hands. To learn more about the potential hazards of nickel arsenide and what precautions to take, consult this guide.