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