Formula: KCa(H3O)3(U6+O2)7(PO4)4O4.8H2O
Phosphate, uranyl mineral, phosphuranylite group
Crystal System: Orthorhombic
Specific gravity:
Hardness: 2½
Streak: Pale yellow
Colour: Bright yellow; deep golden-yellow, honey-yellow
Luminescence: Not fluorescent, but samples may fluoresce due to admixed autunite, etc.

Sedimentary environments

Phosphuranylite is a secondary mineral typically occurring in the weathering zone of pegmatites, coating cracks and fissures near altered uraninite, and in paleochannels (ancient, currently inactive river and stream channels) in sandstone uranium-vanadium deposits. Associated minerals include uraninite, autunite, meta-autunite, uranophane, parauranophane, becquerelite, curite, parsonsite, torbernite, metatorbernite, saleeite, sabugalite, haiweeite and uranium-bearing opal (HOM).

Phosphuranylite typically forms earthy to scaly crusts of minute deep golden yellow crystals. The most common mode of occurrence is an alteration product of uraninite in radioactive pegmatites (Lauf2).


At the Mamões pegmatite, Equador, Rio Grande do Norte, Brazil, phosphuranylite occurs as crystalline to earthy films on quartz with meta-autunite and unidentified uranium minerals (AM 35.756-763).

At Pamplonita, Norte de Santander Department, Colombia, phosphuranylite occurs as earthy films on massive quartz with meta-autunite. Other specimens from this locality show uraninite altering to curite, schoepite, becquerelite and unidentified minerals (AM 35.756-763).

At the Wölsendorf fluorite mining district, Upper Palatinate, Bavaria, Germany, a specimen was found that is a mass of purple-black fluorite, hematite and quartz with fine-grained crusts of a yellow mineral that is a mixture of dewindtite and lead-bearing phosphuranylite (AM 35.756-763).

At the Rosmaneira Mine, Bendada, Sabugal, Guarda, Portugal, phosphuranylite occurs as a thick flaky coating on a slab of deeply altered (?)granite (AM 35.756-763).

At the Carrasca Mine, Quarta-Feira, Sortelha, Sabugal, Guarda, Portugal, veinlets of flaky phosphuranylite cut a slab of altered granite whose outer surfaces are thickly encrusted with meta-autunite. The phosphuranylite is mixed with altered meta-autunite (AM 35.756-763).

At the Urgeiriça Mines, Canas de Senhorim, Nelas, Viseu, Portugal, a specimen was found which was a mass of limonitic quartz with drusy cavities containing citron-yellow to brownish yellow microscopic laths and needles mostly clustered on crystals of a related mineral. The mixture probably represents an intergrowth of lead-bearing phosphuranylite with dewindtite (AM 35.756-763).

At the Fillow Quarry (Branchville Quarry), Branchville, Redding, Fairfield County, Connecticut, USA, phosphuranylite occurs as films and veinlets in altered uraninite (AM 35.756-763).

At Newry, Oxford County, Maine, USA, a large book of muscovite was found containing quartz and uraninite along the margins and coated with phosphuranylite along fracture surfaces and in opened cleavages of the mica (AM 35.756-763).

At the Ruggles Mine, Grafton, Grafton County, New Hampshire, USA, phosphuranylite was found as films and coatings in fractures and cavities in quartz and feldspar, usually near the gummite pseudomorphs after uraninite for which the locality is noted. The phosphuranylite is found with meta-autunite, parsonsite and a number of other secondary uranium minerals. Both phosphuranylite and meta-autunite are particularly abundant at the Ruggles pegmatite, where apatite occurs in large amounts as a primary mineral immediately associated with uraninite (AM 35.756-763).

Phosphuranylite from the Ruggles Mine - Image

At the Palermo mine, North Groton, Grafton County, New Hampshire, USA, coatings of phosphuranylite occur with meta-autunite on aggregates of quartz, muscovite and kaolinised feldspar containing gummite pseudomorphs (AM 35.756-763).

At Bedford Hills, Westchester County, New York, USA, phosphuranylite occurs as minutely crystalline films on feldspar and quartz, with fluorescent hyalite (AM 35.756-763).

The type locality is the Buchanan Mine (Buchanan pegmatite), Mitchell County, North Carolina, USA.

The Flat Rock Mine (Flat Rock pegmatite), Mitchell county, North Carolina, USA, has produced specimens of of smoky or milky quartz, feldspar, muscovite and garnet coated by films of phosphuranylite and meta-autunite. One specimen showed cubical molds of uraninite crystals partly filled with phosphuranylite (AM 35.756-763).

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