Pollucite

It was first described by August Breithaupt in 1846 for occurrences on the island of Elba, Italy. It is named for Pollux, the twin of Castor on the grounds that it is often found associated with petalite (previously known as castorite). The high caesium content was missed by the first analysis by Karl Friedrich Plattner in 1848, but after the discovery of caesium in 1860 a second analysis in 1864 was able to show the high caesium content of pollucite. Its typical occurrence is in lithium-rich granite pegmatites in association with quartz, spodumene, petalite, amblygonite, lepidolite, elbaite, cassiterite, columbite, apatite, eucryptite, muscovite, albite and microcline. About 82% of the world's known reserves of pollucite occur near Bernic Lake in Manitoba, Canada, where they are mined for their caesium content for use in caesium formate oil drilling assistance. This ore is about 20% by weight caesium.

Pollucite is said to be named after Pollux, the immortal son of Zeus in Greek mythology, who was the half-twin of Castor, the mortal son of Tyndareus and for whom the Castorite stone is named. Due to their inseparable nature, Zeus transformed the twins into the constellation Gemini. Similarly, pollucite and Castorite also seem inseparable as they are most often found in the same locations.