Formula: Mg12Mo6+1.33O6(BO3)6F2
Borate, rhabdoborite group, the three rhabdoborite group species form a series, rhabdoborite-(Mo) is a molybdenum-bearing mineral
Crystal System: Hexagonal
Specific gravity: 3.42 calculated
Streak: White
Colour: Light yellow


Rhabdoborite-(Mo) is a relatively new mineral, approved in 2019 and to date (March 2023) reported only from the type locality.


At the type locality, the Arsenatnaya fumarole, Second scoria cone, Northern Breakthrough, Great Fissure eruption, Tolbachik volcano, Kamchatka Krai, Russia, three new borate minerals rhabdoborite-(V), rhabdoborite-(Mo) and rhabdoborite-(W), forming the rhabdoborite group, were found. They are closely associated with each other and with anhydrite, diopside, hematite, schäferite, berzeliite, svabite, calciojohillerite, ludwigite, forsterite, magnesioferrite, baryte, fluorapatite, udinaite, arsenudinaite and powellite. Rhabdoborites form long-prismatic to acicular crystals up to 0.04 × 0.04 × 7 mm3 typically combined in aggregates up to 1 cm. They are transparent, light yellow and with a vitreous lustre (Physics and Chemistry of Minerals 47.44).
The rhabdoborites occur as volcanic sublimates or, more probably, they are formed by the interaction between fumarolic gas and basalt scoria (HOM). They occur in the fumarole, at a depth of 3-4 m below the surface, and at a temperature of 470 to 480oC (Mindat).

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