Calkinsite-(Ce) mineral

Hydrated cerium-dominant rare-earth carbonate mineral with current September 2026 IMA-CNMNC approved formula Ce2(CO3)3·4H2O, status Rn (renamed), and special-procedure tag 1987 s.p. (originally described as calkinsite in 1953 and suffixed in the 1987 IMA rare-earth nomenclature revision; not a numbered IMA approval CURIE). Pecora and Kerr (1953) described the type material (deposited in the U.S. National Museum) from weathered calcite-barite-burbankite veins at the Big Sandy Creek Vermiculite Prospects, Bearpaw Mountains, Hill County, Montana, USA, where it formed by supergene alteration of burbankite alongside lanthanite, ancylite, and barite. Wet-chemical analysis by Marie L. Lindberg on 1.4 g of hand-picked concentrate (~85% calkinsite with minor barite, ancylite, and biotite; Table 5, p. 1178) yielded RE2O3 54.42, CO2 22.40, H2O 12.00, BaO 4.23, SO3 1.58, CaO 1.46, Al2O3 0.97, MgO 0.96, SiO2 0.92, SrO 0.54, Fe2O3 0.47, Na2O 0.26, K2O 0.18, MnO 0.08, total 100.47 wt%; deducting non-essential oxides and combining X-ray fluorescence rare-earth proportions gave the recalculated composition La2O3 19.82, Ce2O3 32.05, Pr2O3 2.89, Nd2O3 7.97, CO2 23.93, H2O 13.34, total 100.00 wt%, corresponding to (Ce1.02La0.64Nd0.25Pr0.09)(CO3)3·4H2O (noting that Table 5 column 3 misprints the La2O3 molar quotient as 0.608 instead of 0.0608, whereas the reported molar sum 0.1909 uses the correct 0.0608 value). Single-crystal Weissenberg and precession X-ray diffraction (Table 3, p. 1175) established an orthorhombic P21221 unit cell with a0 = 9.57(2), b0 = 12.65(8), c0 = 8.94(2) A, V = 1083 A3, Z = 4, and measured specific gravity 3.28(1). Distinct from lanthanite-(Ce) (Ce2(CO3)3·8H2O), ancylite-(Ce), burbankite, and elemental cerium; no criticality designation, microbial mechanism, or industrial recovery yield is asserted.

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Record source: data/records/calkinsite-ce.yaml