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Formula: BaCa6[(SiO4)(VO4)](VO4)2F
Vanadate, zadovite group,
arctite supergroup
Crystal System: Trigonal
Specific gravity: 3.509 calculated from the empirical formula
Hardness: 5 to 5½
Streak: White
Colour: Colourless
Luminescence: No fluorescence has been observed under UV
Environments
Localities
At the type locality, the aradite type locality, Tamar Regional Council, Southern District, Israel, aradite
was found together with zadovite in
paralava veins cutting
gehlenite-rich pyrometamorphic rock formed by the combustion of organic
matter in the sedimentary protolith, or methane released by tectonic forces.
Grains of zadovite and aradite only occur within small veins,
a few centimetres thick, of schorlomite -
rankinite -
pseudowollastonite -
gehlenite paralavas in
fine-grained gehlenite -
larnite rocks. These minerals are generally confined to coarse-grained
rankinite and often occur together. There are three main types of
occurrence of minerals of the zadovite–aradite series:
(1) Grains up to 100–200 µm grown on apatite or enclosed by box-like crystals
of apatite; replacement of apatite
by zadovite is also observed.
(2) Xenomorphic grains 50–100 µm in size developed in the cracks of
rankinite and gehlenite.
(3) Small grains of zadovite–aradite not exceeding 15 µm in size
in ellipsoidal aggregates of finegrained barium-bearing minerals
(baryte, barioferrite,
gurimite, walstromite and
fresnoite), kalsilite and
wollastonite; these are strongly altered to
secondary calcium hydrosilicates.
Occasionally, copper minerals like
cuprite and delafossite form
aggregates together with kalsilite. Compared to
zadovite, aradite is relatively rare. Aradite and
zadovite are associated with the rock-forming minerals
gehlenite,
pseudowollastonite and
wollastonite,
garnet supergroup minerals of the
andradite–schorlomite series,
rankinite, magnesioferrite,
kalsilite and fluorapatite.
Less frequent associates are phosphorus-rich ellestadite,
larnite, cuspidine and
hematite.
The host rocks for aradite and zadovite also display striking
eutectic intergrowths of schorlomite or
gehlenite with a larnite-like
phase on the microscopic level. Accessory minerals include
dorrite–khesinite,
barioferrite, walstromite,
baryte, gurimite,
fresnoite, delafossite,
cuprite, vorlanite,
perovskite and hexacelsian.
The mineral content of the finegrained gehlenite host rocks is not so
complex, mainly comprising gehlenite,
larnite, magnesioferrite and
andradite
(MM 79.1073-1087).
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