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Phosphuranylite
Phosphuranylite
Phosphuranylite
Phosphuranylite

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Phosphuranylite

Specimen Origin: Midnite Mine (Stevens County, Washington, USA)

The Midnite Mine, located northwest of Wellpinit in Stevens County, Washington, was a significant open-pit uranium operation active from the mid-1950s through the early 1980s. It became noted for its variety of secondary uranium minerals formed in oxidized zones and along fracture surfaces. Phosphuranylite from this mine typically appears as bright yellow surface coatings and crusts, often surrounding uraninite and associated with other uranyl phosphates. These specimens are valued both for their rich color and for illustrating secondary uranium mineralization processes in the region.

Phosphuranylite

Phosphuranylite is a hydrous calcium-potassium uranyl phosphate with the formula KCa(H₃O)₃(UO₂)₇(PO₄)₄O₄·8H₂O. It forms vivid yellow to golden coatings and encrustations, sometimes with a resinous or silky luster. The mineral crystallizes in the orthorhombic system, has a Mohs hardness of about 2½, and is strongly radioactive. It develops through supergene alteration of uraninite and pitchblende and is frequently found with related uranyl phosphates such as autunite.