POLLUX, or POLLUCITE, a rare mineral, consisting of hydrous caesium and aluminium silicate, H 2 Cs4AL((Si03)9. Caesium oxide (Cs2O) is present to the extent of 30-36 %, the amount varying somewhat owing to partial replacement by other alkalis, chiefly sodium. The mineral crystallizes in the cubic system. It is colourless and transparent, and has a vitreous lustre. There is no distinct cleavage and the fracture is conchoidal. The hardness is 6| and the specific gravity 2-90. It occurs sparingly, together with the mineral " castor " (see PETALITE), in cavities in the granite of the island of Elba, and with beryl in pegmatite veins at Rumford and Hebron in Maine.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)