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:

Metamorphic environments


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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