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Formula: Th2H(PO4,AsO4)3.6H2O
Phosphate and arsenate, thorium-bearing
mineral
Crystal System: Orthorhombic
Specific gravity: 4.185 calculated
Streak: White
Colour: Brownish pink to salmon pink
Environments
Metamorphic environments
Hydrothermal environments
Thorasphite is a relatively new mineral, approved in 2017 and to date (May 2023) reported only from the type
locality.
Localities
At the type locality, the Elsmore Tin Mine, Elsmore, Gough county, New South Wales, Australia, the deposit is hosted by
folded sediments, dominated by siltstones and
sandstones that have been intruded by high silica
granite. The sediments are overlain, in part, by
basalt. Greisenisation has
resulted in the replacement of feldspars by granular
muscovite and quartz. Following the
development of the greisen, fractures were infilled with
quartz, which carries the tin and other
mineralisation.
Primary minerals are
cassiterite, bismuth and
molybdenite with minor
bismuthinite, arsenopyrite,
ferberite, chalcopyrite and
covellite. The upper part of the deposit is heavily weathered, which led to the
formation of a diverse suite of secondary minerals of
bismuth, molybdenum,
lead, tungsten and
copper in quartz-rich veins and in
granite cavities. The
secondary mineralisation is interpreted to have been formed under
acidic conditions, as suggested by the presence of minerals such as
betpakdalite and rooseveltite.
Thorasphite occurs in cavities in a matrix consisting of quartz and
muscovite. The only directly associated mineral is
jarosite. Crystals of monazite-(Ce)
occur in adjacent cavities in the matrix and are the likely source of thorium for
thorasphite, although thorium is not an essential constituent of
monazite-(Ce). The thorasphite occurs as brownish pink to salmon pink,
prismatic to acicular crystals up to 0.08 mm in length and
0.002 mm across
(CM 60.719-727).
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