Phurcalite

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Formula: Ca₂(UO₂)₃O₂)(PO₄)₂.7H₂O
Hydrated phosphate, phosphuranylite group
Crystal System: Orthorhombic
Specific gravity: 4.22 measured, 4.220 calculated
Hardness: 3
Streak: Yellow-white
Colour: Yellow
RADIOACTIVE
Environments

Plutonic igneous environments
Pegmatites

Phurcalite occurs as a secondary mineral in cracks and fractures in granite and granite pegmatites. Associated minerals include autunite, meta-autunite, uranophane and other secondary uranium minerals (HOM).

Localities

At Perus, São Paulo, São Paulo, Brazil, phurcalite fills in fractures of the tourmaline-bearing granitic pegmatite. In the one hand specimen studied, no other uranium mineral is directly associated with phurcalite, but several other uranium minerals occur in the pegmatite fractures, including autunite, meta-autunite, chernikovite, torbernite, metatorbernite, phosphuranylite, uranophane, uranophane-β and haiweeite. Phurcalite is considered to be a secondary mineral, and the product of hydrothermal activity with a temperature of formation not exceeding 150^o (CM 29.95-105).

At Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic, phurcalite was found on a few specimens originating from the dump material of the Eduard shaft. Phurcalite forms yellow to yellowish-orange prismatic crystals up to 4 mm in cavities of vuggy quartz-dominated gangue. Associated minerals include walpurgite, uranophane-α, and members of the metatorbernite-metazeunerite series (Bulletin of Mineralogy and Petrology, 28, 276-280).

At the type locality, the Streuberg Quarry, Bergen, Vogtlandkreis, Saxony, Germany, phurcalite is associated with specular hematite (AM 64.243).

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