pollucitebearing

Pollucitebearing describes rocks or mineral assemblages that contain pollucite, a cesium-rich aluminosilicate mineral with the chemical formula CsAlSi2O6. Pollucite is most commonly found in granitic pegmatites and related hydrothermal veins formed during late-stage crystallization. The term is used to designate pegmatitic rocks or suites in which pollucite is a major or conspicuous constituent.

Geology and occurrence: Pollucite-bearing pegmatites are highly enriched in lithophile elements such as Cs, Li, Rb, Ta, and Nb and often host other Cs minerals such as amblygonite, eucryptite, and lepidolite, together with feldspars, quartz, spodumene, beryl, and rarely apatite. Pollucite typically occurs as well-formed crystals or massive aggregates within cavities, fractures, or vesicles in pegmatites.

Formation and petrology: Pollucite forms during extreme late-stage differentiation of granitic melts, when Cs becomes concentrated in the residual melt phase and is transported by volatile-rich fluids into crystallization pockets. The presence of pollucite indicates a highly evolved, Cs-enriched system and is a key indicator of Cs mineralization potential.

Economic significance: Pollucite is the principal ore of cesium, a metal used in various industrial applications including catalysts, glass, and cesium formate. Pollucite-bearing pegmatites are mined where abundance and grade justify extraction; cesium content can vary widely among deposits.

Identification: In hand sample and thin section, pollucite is typically colorless to pale, sometimes yellowish, with a glassy luster. It crystallizes in a tectosilicate framework and is distinguished by X-ray diffraction and electron microprobe analysis. See also cesium minerals and pegmatites.