Bayleyite Locality: Ambrosia Lake area, Grants District, McKinley County , New Mexico , USA ( Locality at mindat.org ) Size: miniature, 4.6 x 2.4 x 1.6 cm Bayleyite A large and rich specimen of this rare magnesium and uranium carbonate species, hard to come by! In fact, this is the only one I have ever had. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Bayleyite
A bright-yellow hydrated magnesium uranyl carbonate — a secondary uranium mineral.
Intro adapted from Wikipedia (CC BY-SA).
Bayleyite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Mg₂(UO₂)(CO₃)₃·18H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/a).
Key properties: Mohs hardness 2–2.5; specific gravity 2.05; Vitreous, dulling with dehydration luster; refractive index 1.482; optically biaxial.
IMA symbol Byy, grandfathered status — known before the IMA’s founding, named in 1951.
Found as a coating or efflorescence with other secondary uranium minerals, which may be post-mining, typically in sediment-hosted uranium-bearing deposits.
It is found associated with Schröckingerite, andersonite, swartzite, gypsum (Hillside mine, Arizona, USA); schröckingerite, gypsum (Hideout mine, Utah, USA); tyuyamunite, uranophane.
The mineral was named to honor Professor William Shirley Bayley (1861–1943), American mineralogist and geologist, University of Illinois, Urbana, Illinois, USA, and the U.S. Geological Survey.