Pollucite

Pollucite is a rare gem mineral belonging to the group of zeolites. It contains a large amount of cesium and sometimes rubidium.

Pollucite forms transparent colorless cubes, dodecahedrons or trapezoids and can also occur as fine-grained materials.

Mohs hardness on a scale of 6.5 to 7. It was first described by August Breithaupt in 1846 for occurrences on the island of Elba in Italy. Named after Pollux, a figure from Greek mythology, Castor's brother, for his joint connection with the "castorite" (petalite). The name was later changed to the current pollucite.

It is most commonly found in lithium-rich granite pegmatites in association with quartz, bottomstone, petalite, amblygonite, lepidolite, elbaite, cassiterite, columbite, apatite, eucryptite, muscovite, albite and microcline.