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Formula: CaUO4
Oxide, uranium-bearing mineral
Crystal System: Isometric
Specific gravity: 7.29 calculated for the empirical formula
Hardness: 4 to 5
Streak: Dark brown to cherry-red
Colour: Black
Solubility: Soluble in 10% hydrochloric acid at room temperature
Common impurities:
RADIOACTIVE
Environments
Localities
At the type locality, Xenolith no. 7, Lakargi Mountain, Upper Chegem volcanic caldera, Baksan Valley,
Kabardino-Balkaria, Russia, vorlanite is an accessory mineral in the heavily altered
skarn composed of millimetre-sized lenses of
larnite with rondorfite and
wadalite inclusions. Larnite occurs
partially replaced by chegemite,
reinhardbraunsite and minerals of the
fluorellestadite-hydroxylellestadite
series. White-greyish lenses of larnite are embedded in the yellow mass of
secondary
katoite-hibschite,
afwillite, hillebrandite,
bultfonteinite,
hydrocalumite,
ettringite group minerals, and minute spots of
hematite.
Vorlanite is locally associated with elbrusite,
uranium-bearing lakargiite,
perovskite and srebrodolskite.
Skarns with abundant
secondary low-temperature minerals are enriched in
vorlanite, potentially suggestive of vorlanite being a low-temperature mineral. However, rare
vorlanite occurrences in only slightly altered rock fragments, together with other high-temperature minerals such
as larnite, chegemite,
reinhardbraunsite,
rondorfite, wadalite,
fluorellestadite and
hydroxylellestadite confirm vorlanite’s high-temperature
genesis.
Platy crystals of vorlanite up to 300 µm across and 15–20 µm thick commonly form sheaves. Vorlanite
crystals have xenomorphic form with rare outgrowths of platelets having hexagonal outlines. Vorlanite is black
with a submetallic lustre and dark brown to cherry-red streak. In thin section it is translucent, brownish-red. In
reflected light it is light grey with brown or red internal reflections
(AM 96.188-196).
Vorlanite from the Lakargi Mountain - Image
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