Blatonite, UO2CO3 center dot H2O, a new uranyl carbonate monohydrate from San Juan County, Utah

Blatonite, ideally UO2CO3. H2O, is a new uranyl carbonate mineral found in the Jomac mine, Brown's Rim, San Juan County, Utah. It occurs in seams of g ypsum located between some bedding planes of a layer of siltstones within t he Triassic Shinarump conglomerate. Associated U6+ minerals are boltwoodite , coconinoite, metazeunerite, and rutherfordine, together with the Cu2+ min erals azurite, brochantite, carbonate-cyanotrichite and malachite. Blatonit e occurs as acicular crystals that are canary yellow and translucent with a silky luster and colorless streak. It strongly fluoresces in UV. H-Mohs = 2-3. D-meas. = 4.05(2), D-calc. = 4.02 g/cm(3) (idealized formula). Optical ly uniaxial(+), omega 1.588(2), epsilon 1.612(2). The crystals are nonpleoc hroic. Blatonite is hexagonal or trigonal (space group unknown): a 15.79(1) , c 23.93(3) Angstrom, V 5167(9) Angstrom(3) and Z = 36. The strongest refl ections of the X-ray powder pattern [d(in Angstrom)(I)hkl] are: 7.86(47)110 , 6.91(55)103, 6.56(77)201, 4.76(40)114, 4.34(36)213 and 3.06(100)207. Elec tron microprobe and thermogravimetric analyses gave UO3 81.98, CO2 12.82, H 2O 5.38, total 100.18 wt %. The empirical formula is 0.988 UO2. 1.004 CO2. 1.029 H2O. The name honors the Belgian crystallographer Norbert Blaton, Uni versity of Leuven, Belgium. Holotype material is deposited in the mineralog ical collection of the Royal Belgian Institute of Natural Sciences, Brussel s, Belgium.