Bayleyite

Mg2 (UO2 )(CO3 )3 • 18H2 O
c 2001-2005 Mineral Data Publishing, version 1

Crystal Data: Monoclinic. Point Group: 2/m. Crystals are well-formed, short prismaticalong [001], to 0.1 mm; typically in globular aggregates and crusts of divergent crystals.
Physical Properties: Fracture: Conchoidal. Hardness = 2–2.5 D(meas.) = 2.05
D(calc.) = 2.06 Radioactive. Soluble in H2 O; may rapidly dehydrate; weak fluorescence of
uncertain yellow-green to pale greenish under LW and SW UV.
Optical Properties: Semitransparent. Color: Sulfur-yellow. Luster: Vitreous, dulling withdehydration.
Optical Class: Biaxial (–). Pleochroism: X = pale pink; Y = Z = pale yellow to greenish yellow.
Orientation: Z = b; X ∧ c = 8◦ –15◦ . α = 1.454–1.455 β = 1.490–1.492 γ = 1.500–1.502
2V(meas.) = 30◦ 2V(calc.) = 45◦ –57◦
Cell Data:
Z=4Space Group: P 21 /a. a = 26.65(5)b = 15.31(5)c = 6.53(2)β = 93◦ 040

X-ray Powder Pattern: Hillside mine, Arizona, USA.
7.66 (10), 13.1 (9), 3.83 (6), 2.69 (5), 2.21 (5), 6.53 (4), 5.85 (4b)Chemistry:
UO3SO3CO2MgO

(1)
35.28
0.02
16.72
9.76

(2)
34.76
16.04
9.80

Na2 O
K2 O
H2 O

(1)
0.21
0.10
37.91

(2)

39.40

Total [100.00]
100.00(1) Hillside mine, Arizona, USA; recalculated from an original total of 100.78%, after deductionof gypsum 8.45% and insoluble 0.45%; corresponds to Mg2.00 (UO2 )1.02 (CO3 )3.15 • 17.43H2 O.
(2) Mg2 (UO2 )(CO3 )3 • 18H2 O.
Occurrence: As a coating or efflorescence with other secondary uranium minerals, which may
be post-mining, typically in sediment-hosted uranium-bearing deposits.
Association: Schröckingerite, andersonite, swartzite, gypsum (Hillside mine, Arizona, USA);schröckingerite, gypsum (Hideout mine, Utah, USA); tyuyamunite, uranophane, liebigite, carnotite(Powder River Basin, Wyoming, USA).
Distribution: In the USA, in Arizona, from the Hillside mine, about 5.5 km north of Bagdad,
Eureka district, Yavapai Co., and in the Cole shaft, Bisbee, Cochise Co.; at Ambrosia Lake,Grants district, McKinley Co., New Mexico; in Utah, from the Hideout No. 1 (Tiger) mine, DeerFlats, White Canyon district, on the Coral claim, Elk Ridge, at the Mi Vida mine, San Juan Co.,and from the Delta Group mine, San Rafael Swell, Emery Co.; in Colorado, at the Garfield andRifle mines, north of Rifle, Garfield Co., from the J.J. mine, Montrose Co., and well-crystallized
in the Schwartzwalder mine, Jefferson Co.; in Wyoming, from the Pumpkin Buttes area, PowderRiver Basin, Niobrara Co. In the Rabbit Lake uranium mine, Saskatchewan, Canada. From nearAzegour, Morocco. In the Huemul mine, Malargüe district, Mendoza Province, Argentina. From
the Mas-d’Alary uranium deposit, three km south-southeast of Lodève, Hérault, France. In theHatrurim Formation, Israel.
Name: To honor Professor William Shirley Bayley (1861–1943), American mineralogist andgeologist, University of Illinois, Urbana, Illinois, USA, and the U.S. Geological Survey.
Type Material:

National Museum of Natural History, Washington, D.C., USA, 106101–106104.

References: (1) Palache, C., H. Berman, and C. Frondel (1951) Dana’s system of mineralogy,(7th edition), v. II, 237–238. (2) Frondel, C. (1958) Systematic mineralogy of uranium andthorium. U.S. Geol. Sur. Bull. 1064, 112–115. (3) Weeks, A.D. and M.E. Thompson (1954)
Identification and occurrence of uranium and vanadium minerals from the Colorado Plateaus.
U.S. Geol. Surv. Bull. 1009-B, 25–26. (4) Axelrod, J.M., F.S. Grimaldi, C. Milton, andK.J. Murata (1951) The uranium minerals from the Hillside mine, Yavapai County, Arizona.
Amer. Mineral., 36, 1–22. (5) Z.Y. Zhang, K.D. Luo, and Z.R. Chen (1985) The crystal structureof bayleyite. Scientica Sinica, Series B, 28(4), 344–350.
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