Surname for New Gemstone

By Gary Roskin, G.G., FGA, Senior Editor -- JCK Online, 3/1/2004 2:00:00 AM

Saturated orangy-pink cesium-rich beryl from Madagascar isn't just another pretty pink morganite, according to the International Mineralogical Association (IMA). Because of its unique properties, the new gem is its own mineral, a new beryl variety called pezzottaite (pronounced "pe-ZO-ta-ite"). Drs. Henry Hänni and Michael Krzemnicki of the Swiss Gemological Institute (SSEF) discovered the gem's properties and reported on the Madagascar find as well as on Afghan pezzottaite.

Every variety of the beryl species is classified as a beryllium aluminum silicate, made from four basic elements—beryllium, aluminum, silicon, and oxygen. In its pure state, beryl is colorless. That variety is called goshenite. When enough trace elements of chromium and/or vanadium are present, the result is a saturated green gem called emerald. (Faint to lightly colored green beryl is called simply green beryl.) Yellow beryls and blue beryls—variety names heliodor and aquamarine, respectively—get their color from trace amounts of iron. Morganite, a light pink beryl, gets its color from manganese.

The new saturated pink beryl derives its color from cesium and lithium rather than manganese, but the differences between it and morganite go beyond chemistry and color. Pezzottaite is also higher in specific gravity (density) because cesium accounts for nearly 14% of its weight. Morganite normally contains only a small amount of cesium, approximately 1%. In addition, pezzottaite's refractive index (ability to bend light) of 1.608-1.615 is higher than morganite's 1.587-1.596. (RI for beryl is typically around 1.58.)

Pezzottaite's properties, including its typical tube-like inclusions, make the new beryl look more like pink tourmaline (which has an RI of 1.62-1.64) than pale/pastel pink morganite. However, pezzottaite's birefringence of .007 is far from tourmaline's .020, which produces easily visible doubling.

According to Tom Cushman, Sun Valley, Idaho, who imports gems from Madagascar and introduced the cesium-rich beryl last year in Tucson, there were only two pockets of material found in one mine site at Mandrosonoro, and none has been found since. According to H™nni, there is a similar single find in Afghanistan (9% cesium content).

On Sept. 5, 2003, the new Madagascar gem was named after Dr. Federico Pezzotta, a very active Italian mineralogist, a specialist in Madagascan gems, and curator of the Natural History Museum in Milan.