POLLUCITE

    Class : Silicates
    Subclass : Tectosilicates
    Crystal system : Cubic
    Chemistry : (Cs,Na)(AlSi2)O6 nH2O
    Rarity : Uncommon to rare


Although rare, pollucite, belonging to the zeolite group, is the most common cesium mineral. The substitution of cesium by sodium is at the origin of a series with analcime. It is an accessory mineral of sodolithic pegmatites which most often forms veinlets or compact xenomorphic masses of sometimes imposing dimensions (several tonnes). It commonly accompanies microcline, petalite, spodumene, lepidolite, elbaite and beryl. Its name is inspired by the character from Greek mythology Pollux, twin brother of Castor, son of Zeus and Leda because this mineral is commonly found in association with castorite (now known as petalite). Pollucite crystals are rare and frequently corroded. Translucent to transparent, pollucite is colorless to white, bluish or pinkish, with a marked vitrous luster. Massive, it is not easy to distinguish from feldspars. Pollucite is the only cesium mineral that does not suffer from extreme rarity. However, it is too common to constitute a real ore and cesium is mainly extracted from more common minerals where it is present in small quantities, notably feldspars or micas. Some transparent pollucite are cut as fine gemstones.

Main photo : Pollucite from Skardu, Gilgit-Baltistan, Pakistan © Dan Weinrich

Pollucite from Skardu, Gilgit-Baltistan, Pakistan © Jose Zendrera
Pollucite from Paprok, Afghanistan © Rob Lavinsky
Pollucite gem from Ognevka Ta, Kazakhstan © Bertil Otter
0.76ct pollucite from Afghanistan

Pollucite in the World

The Tanco pegmatites are undoubtedly the site having delivered the most phenomenal quantities of pollucite, with crystals exceeding 2 meters and large clusters of several thousand tonnes (including one measuring 180 x 75 x 12 meters). The Helicon site, near Karibib (Namibia) also provided masses of impressive size. The pollucite clusters encountered in Californian pegmatites are much more modest in size (a few cubic decimeters). The best sites for crystallized pollucite are the pegmatites of San Piero in Campo (Island of Elba, Italy), where the crystals reach 6 cm, of Paprok and Kamdesh (Afghanistan) with extraordinary crystals of 50 cm associated with elbaite, as well as Shingus and Skardu (Pakistan) who produced perfect 10 cm crystals on albite and muscovite.

Pollucite in France

Pollucite is not present in the French underground.

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.



Hardness : 6.5
Density : 2.9
Fracture : Sub-conchoidal
Streak : White


TP : Translucent to transparent
RI : 1.517 to 1.525
Birefringence : 0
Optical character : None
Pleochroism : None
Fluorescence : Sometimes yellow


Solubility : Acids

Magnetism : NoneRadioactivity : None

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