Pollucite is a very rare cesium mineral. In fact, it is the only mineral in which Cs is an essential constituent. Gems are always very small, under 10 carats, despite the existence of large beds at some localities.
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|Crystallography||Isometric. Crystals cubic, very rare; massive, fine-grained.|
|Colors||Colorless, white, gray; tinted pale pink, blue, violet.|
|Luster||Vitreous, slightly greasy.|
|Cleavage||None. Fracture conchoidal. Brittle.|
|Stone Sizes||Masses in South Dakota reach 3-4 feet in thickness, opaque, whitish. Gems are usually colorless and very small; Maine material cuts stones from masses that reach a size of 10 inches. Smithsonian Institution (Washington, D.C): 8.5 (colorless, Maine); 7.0 (colorless, Connecticut). Private Collection: 3.85 (pinkish, Maine).|
|Luminescence||Orange to pink ﬂuorescence in UV and X-rays.|
|Formula||Cs1-xNa,AlSi2O6· xh2O; x ~ 0.3. Also written; (Cs,Na)2(Al2Si4)O12 · H2O.|
Series to Analcime; Zeolite Group.
Optics: Isotropic; N: 1.518-1.525.
Inclusions: Usually whitish, resembling spikes or balls, very small; also very tiny snowflakes, bulging at the centers.
Occurrence: In granite pegmatites.
San Diego County, California; Middletown, Connecticut.
Bernie Lake, Manitoba, Canada; Elba, Italy; Finland;
Kazakhstan, USSR; Karibib, Namibia.
Custer County, South Dakota: massive material in thick seams.
Newry, Maine: gem material.
Various localities in Maine and Massachusetts.
Varutrask, Sweden: massive lilac to white material (1.518, S.G. 2.90).
Comments: Pollucite is a very rare cesium mineral. In fact, it is the only mineral in which Cs is an essential constituent. Gems are always very small, under 10 carats, despite the existence of large beds at some localities.
It is colorless and lacks fire when cut but is of interest for its great rarity.
Name: Pollux was, along with Castor, a brother of Helen of Troy in Greek mythology. This mineral was found in Italy in 1846, and named pollux; it was associated with another mineral, named castor: which was later studied and renamed petalite.