Rhabdoborite-(W)
Rhabdoborite-(W) is an IMA-recognized mineral species in the borate class, with the chemical formula Mg₁₂(W⁶⁺,V⁵⁺)₁.₅O₆{[BO₃]₆₋ₓ[(P,As)O₄]ₓF₂₋ₓ} (x < 1).
It crystallizes in the hexagonal crystal system (space group P6_3). It is a member of the Rhabdoborite structural group.
Key properties: specific gravity 3.59; White streak; Vitreous luster; optically uniaxial.
IMA symbol Rbo-W, IMA status: approved, named in 2018.
A volcanic sublimate or, more probably, formed by the interaction between fumarolic gas and basalt scoria.
It is found associated with Rhabdoborite-(V), rhabdoborite-(Mo), anhydrite, diopside, hematite, schäferite, berzeliite, svabite, calciojohillerite, ludwigite, forsterite, magnesioferrite.
Refers to morphological (rhabdos is “rod”, in Greek) and chemical (borate) features of the mineral; a suffix indicates the dominant element as the M component.