Muséum national d'histoire naturelle _ The species

FROM : Afghanistan
SIZE : 9.5 x 9 x 7 cm

This sample is a pollucite crystal on which one observes an elbaite cystal. Pollucite is white almost opaque, crystal of elbaite gem is biterminated. It shows many colours: redish orange at extrmities and pale pink, green yellow and pale yellow towards centre.

One notes absence of another elbaite crystal which has vanished (most likely at the moment of the minig of the pollucite crystal).

This sample, acquired thanks to support from Total, comes from Afghanistan. It is kept in the storage rooms of the collections of the Muséum national d'Histoire naturelle (i.e., not yet displayed to the public).

Photography and 3D view: A. Dahmane / Photo Saint-Hilaire, © MNHN.

SPECIE : Pollucite

HISTORY : Name inspired by the Greek mythology where Pollux is the brother of Castor, in reference to its association with castorite (ancient name of petalite)

Species first described in 1846 by Johann Friedrich August Breithaupt (1791-1873), German mineralogist

Type-locality: Monte Capanne, Elba Island, Tuscany

CHEMICAL FORMULA : (Cs,Na)(AlSi2)O6 nH2O
CRYSTAL SYSTEM : Cubic
COLOR : Colourless, white, gray, pink, blue, violett
DIAPHANIETY : Transparent to translucent
LUSTER : Vitreous to greasy
STREAK : White
MORPHOLOGY : Cubic crystals, dodecahedric, striated
HARDNESS : 6,5-7,0
DENSITY : 2,94

CHEMICAL CLASS : VIII - Silicates
GROUP : Analcime
STRUNZ CLASS BEFORE 2001 : 8/J.27-20
STRUNZ CLASS AFTER 2001 : 9.GB.05

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