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Formula: Mg12W6+1.33O6(BO3)6F2
Borate, rhabdoborite group,
the three rhabdoborite group members constitute a series
Crystal System: Hexagonal
Specific gravity: 3.59 calculated
Streak: White
Colour: Light yellow, beige
Environments
Rhabdoborite is a relatively new mineral, approved in 2018 and to date (September 2023) reported only from the
type locality.
Localities
At the type locality, the Arsenatnaya fumarole, Second scoria cone, Northern Breakthrough, Great Fissure
eruption, Tolbachik Volcanic field, Milkovsky District, Kamchatka Krai, Russia, three new
borate minerals,
rhabdoborite-(V),
rhabdoborite-(Mo) and rhabdoborite-(W) 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).
They occur in the fumarole, at a depth of 3 to 4 m below the surface, and at a temperature of 470 to 480°C
(Mindat).
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