Mineral Information and Data:

Mg2(UO2)(CO3)3(H2O)12 • 6H2O [CNMNC approved formula]

Named for William Shirley Bayley (1861-1943), American mineralogist and geologist, University of Illinois, Urbana, Illinois, USA.

IMA status : Valid species (Pre-IMA 1948) Grandfathered
(8th edition) :  
  (15) Hydrated Carbonates
  (15.03) where A+m B++n (XO3)p · x(H2O), (m+n):p = 1:1 and containing U, Th, Zr, Y
(10th edition) :
  (05) Carbonates and Nitrates
  (05.E) Uranyl Carbonates
  (05.ED) UO2:CO3 = 1:3
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Space group: P21/a
Unit cell: a = 26.65Å, b = 15.31Å, c = 6.53Å β = 93.07°
Crystal Habit: Crystals are well-formed, short prismatic along [001], to 0.1 mm; typically in globular aggregates and crusts of divergent crystals.
Color: Sulfur-yellow
Diaphaneity: Semi-transparent
Luster: Vitreous, dulling with dehydration
Hardness (Mohs): 2 - 2.5
Fracture: Conchoidal
Geologic Setting: As a coating or efflorescence with other secondary uranium minerals, which may be post-mining, typically in sediment-hosted uranium-bearing deposits.
Mineral Association: Schrockingerite, andersonite, swartzite, gypsum (Hillside mine, Arizona, USA); schrockingerite, gypsum (Hideout mine, Utah, USA); tyuyamunite, uranophane, liebigite, carnotite (Powder River Basin, Wyoming, USA).
Luminescent Properties: Weak fluorescence of uncertain yellow-green to pale greenish under LW and SW UV.
Other Properties: Radioactive. H2O Soluble.
Comments: May rapidly dehydrate.