Because of the intensive colors and the apparent hexagonal crystallization, initial speculation suggested a new form of Bixbite. The mood was exuberant as bixbite is the most rare and valuable crystallization of beryl. Bixbite is never available in large sizes and prices for even 3 carat stones exceed the best Colombian emeralds in a similar size range.
But careful examination showed that although Pezzottaite crystallized with a resemblance to Beryl, it wasn’t exactly the same, and could not be Beryl. More specifically Pezzottaite is trigonal in nature and Beryl is hexagonal. Trigonal crystallization is 3-fold in symmetry while hexagonal crystallization is 6-fold. The similarity is such that some literature even considers the trigonal classification to be a subsystem of hexagonal crystallization.
Indeed, Pezzottaite was originally considered to be a cesium rich beryl but Pezzottaite also contains lithium and this ordered incorporation of lithium into the crystal lattice is responsible for the crystallization dissimilar to beryl. Like morganite and bixbite, pezzottaite is believed to owe its color to natural radiation-induced color centers involving trivalent manganese ions.
With a refractive index up to 1.615 and a density up to 3.10, these values also exceed the properties for beryl. Chemical analyses have revealed very high cesium concentrations of over 15% Cs2O. With the exception of hardness, the physical and optical properties of pezzottaite including its specific gravity of 3.10 (average) and refractive index 1.601 - 1.620 are all higher than typical beryl.
Pezzottaite, was initially marketed as bixbite by unknowing or unscrupulous sellers and also under the name raspberyl or raspberry beryl. In September 2003 it was formally identified recognized by the International Mineralogical as mineral species and named after a well known Italian geologist and mineralogist Federico Pezzotta. Its chemical formula is Cs(Be2Li)Al2Si6O18.
Colors include shades of raspberry red to orange-red and the crystals are tabular in habit. Pleochroism is moderate, from pink-orange or purplish pink to pinkish purple.
Most of the stones are heavily included with growth tubes and or liquid feathers and some 10% of the rough may also exhibit chatoyancy when polished. Cut stones are usually small and rarely exceed two carats. Pezzottiate is brittle with a conchoidal to irregular fracture. Like beryl, it possesses an imperfect basal cleavage. Pezzottaite will lose its color if heated to 450 °C for two hours, but the color can be restored with gamma irradiation.
Most if not all of the Madagascan Pezzottaite deposits have already been exhausted. Pezzottaite has also been found in at least one other locality in Afghanistan where it was also initially thought to be beryl.
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