rammelsbergite

{{Infobox mineral | name = Rammelsbergite | boxwidth = | image = Rammelsbergite-180028.jpg | imagesize = 260px | alt = | caption = | category = | formula = NiAs2 | IMAsymbol = Rmb | molweight = | strunz = 2.EB.15a | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pnnm | unit cell = a = 4.759 Å, b = 5.797 Å c = 3.539 Å; Z = 2 | color = Tin white with a faint pinkish hue | colour = | habit = Rarely as prismatic crystals; commonly massive, granular, radial, fibrous | twinning = On {101} | cleavage = Distinct on {101} | fracture = Irregular | tenacity = Brittle | mohs = 5.5–6 | luster = Metallic | streak = Grayish black | diaphaneity = Opaque | gravity = 7.0–7.1 | density = | polish = | opticalprop = Strongly anisotropic | refractive = | birefringence = | pleochroism = Weak, yellow to pinkish hue and bluish white | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Rammelsbergite is a nickel arsenide mineral with formula NiAs2. It forms metallic silvery to tin white to reddish orthorhombic prismatic crystals, and is usually massive in form. It has a Mohs hardness of 5.5 and a specific gravity of 7.1.