bunsenite

Bunsenite is a rare natural mineral consisting of nickel oxide with the chemical formula NiO. It is one of the few oxide minerals that occur in nature as a distinct phase and is named for the German chemist Robert Bunsen.

In hand specimen it appears as black to brownish-black, opaque grains or crystals with a metallic to submetallic luster. Crystallography places bunsenite in the cubic system, adopting the rock-salt structure typical of NiO.

Formation and occurrence: Bunsenite forms as an oxidation product of nickel-bearing minerals, most often in ultramafic and nickel-rich ore environments. It can occur as inclusions or intergrowths with other nickel minerals and oxides. It has been reported from several localities worldwide, though it remains rare.

Identification and related minerals: It is distinguished by its nickel oxide composition, cubic symmetry, and association with other nickel-bearing minerals such as nickel sulfides and other oxides. Analytical techniques include X-ray diffraction and chemical analysis.

Significance: Bunsenite is of interest mainly to mineralogists and collectors; industrially nickel oxide materials are widely used, but bunsenite as a naturally occurring phase is not a common industrial source.