From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Bayleyite sample from the Ambrosia Lake area, Grants District, New Mexico (size: 4.6 x 2.4 x 1.6 cm)
CategoryCarbonate mineral
(repeating unit)
IMA symbolByy[1]
Strunz classification5.ED.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/c
Unit cella = 26.65 Å, b = 15.31 Å,
c = 6.53 Å; β = 93.07°; Z = 4
ColorSulfur yellow
Crystal habitClusters of prismatic crystals, crusts
Mohs scale hardness2 - 2.5
Specific gravity2.05
Optical propertiesBiaxial (-)
Refractive indexnα = 1.453 - 1.455 nβ = 1.490 - 1.492 nγ = 1.498 - 1.502
Birefringenceδ = 0.045 - 0.047
PleochroismVisible: X = Pinkish, Y = Light yellow, Z = Light yellow
2V angleMeasured: 30°
Ultraviolet fluorescenceWeak; yellow-green to pale greenish under LW and SW
Other characteristicsRadioactive.svg Radioactive

Bayleyite is a uranium carbonate mineral with the chemical formula: Mg2(UO2)(CO3)3·18(H2O). It is a secondary mineral which contains magnesium, uranium and carbon. It is a bright yellow color. Its crystal habit is acicular but is more commonly found as crusts on uranium bearing ores. It has a Mohs hardness of about 2-2.5.[2]


It was first described in 1948 for an occurrence in the Hillside mine, north of Bagdad, Yavapai County, Arizona and named for mineralogist William Shirley Bayley (1861–1943) of the University of Illinois. It occurs as an efflorescence or coating on other secondary minerals and often is deposited on mine walls and workings. It occurs with schrockingerite, andersonite, swartzite and gypsum in the Hillside mine; with schrockingerite and gypsum in the Hideout mine in Utah; and with tyuyamunite, uranophane, liebigite and carnotite in the Powder River Basin in Wyoming.[4]


  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b Bayleyite on
  3. ^ Bayleyite on Webmineral
  4. ^ a b Handbook of Mineralogy