Ranunculite

ranunculite

Images

Formula: Al(UO₂)(PO₃OH)(OH)₃.4H₂O
Valence: Al(U⁶⁺O₂)(PO₃OH)(OH)₃.4H₂O Hydrated phosphate, uranyl mineral
Crystal System: Monoclinic
Specific gravity: 3.40 measured, 3.4042 calculated
Hardness: 3
Streak: Pale yellow
Colour: Golden yellow
Luminescence: No fluorescence under UV
Solubility: Slowly soluble in 1:1 nitric acid and fairly soluble in hot 1:1 hydrochloric acid
Very strongly RADIOACTIVE
Environments

Pegmatites

Localities

At the type locality, the Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo, ranunculite occurs in uranium-rich portions of the granite pegmatite that was mainly worked for beryl and columbite. Minerals associated with ranunculite in the yellow coatings of the rock include meta-autunite, phosphuranylite, phuralumite, upalite, and threadgoldite.
Ranunculite occurs as gold-yellow nodules typically 0.3 mm across; larger sizes up to 1 mm are unusual. The nodules may be contiguous, then forming botryoidal crusts. Ranunculite is not fluorescent but several samples are covered by a white coating that fluoresces green under UV. The nodules may carry millimetre-sized crystals of canary-yellow prisms of phuralumite. Ranunculite is relatively abundant in the specimens from the uraniferous zone of the Kobokobo pegmatite (MM 43.321-323).
Ranunculite from the Kobokobo pegmatite - Image

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