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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 150o
(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).
Phurcalite from Streuberg - Image
At the Posey Mine, Red Canyon Mining District, San Juan County, Utah, USA, phurcalite has been found with
brochantite
(Mindat photo).
Phurcalite from the Posey Mine - Image
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