Meyrowitzite, Ca(UO2)(CO3)25H2O, a new mineral with a novel uranyl-carbonate sheet

Abstract

Meyrowitzite, Ca(UO2)(CO3)25H2O, is a new mineral species from the Markey mine, Red Canyon, San Juan County, Utah, U.S.A. It is a secondary phase found on calcite-veined asphaltum in association with gypsum, markeyite, and rozenite. Meyrowitzite occurs as blades up to about 0.2 mm in length, elongate on [010], flattened on 100, and exhibiting the forms 100, 001, 101, 110, and 011. The mineral is yellow and transparent with vitreous luster and very pale yellow streak. Fluorescence under a 405 nm laser is from weak greenish yellow to moderate greenish blue. The Mohs hardness is ca. 2, tenacity is brittle, fracture is irregular, and there is one perfect cleavage, 101. The measured density is 2.70(2) g/cm3. The mineral is optically biaxial (+) with α = 1.520(2), β = 1.528(2), and γ = 1.561(2) (white light). The 2V(meas) = 53.0(6)°; weak dispersion, r > ν; optical orientation: Z = b, Y - a = 19° in obtuse β; pleochroism pale yellow, X Y 2σI) contains both UO7 pentagonal bipyramids and UO8 hexagonal bipyramids, the latter participating in uranyl tricarbonate clusters (UTC). The two kinds of bipyramids and the carbonate groups link to form a novel corrugated heteropolyhedral sheet. This is the first structural characterization of a uranyl-carbonate mineral with a U:C ratio of 1:2. Meyrowitzite is apparently dimorphous with zellerite.