Cat's Eye Pezzottaite
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Cat's eye pezzottaite, sold as crimson or crimson beryl.
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crimson cat's eye
This is a new mineral species. I was first recognized by the International Mineralogical Society in September 2003. Pezzottaite is the cesium equivalent of beryllium. Cesium silicate, as well as beryllium, lithium and aluminum. With the chemical formula Cs(Be2Li)Al2Si6O18.
It is named after the Italian geologist and mineralogist Federico Pezzotta. Pezzottaite was originally thought to be red beryl. Or a new variety of beryllium: cesium beryllium. However, unlike real beryllium, pezzottaite contains lithium and crystallizes. It is in a trigonal crystal system, not a hexagonal one.
The color scheme includes shades of crimson red, orange red and pink. It is extracted from merolithic quarries in the granite pegmatite deposits of the province of Fianarantsoa in the south of Madagascar. The pezzottaite crystals were small, no larger than about 7 cm/2.8 inches, at their widest size, and had a tabular or equivalent shape.
And some, most of them are strongly associated with growth tubes and liquid feathers. About 10 percent of the rough material also became verbose after polishing. Most pezzottaite cut gemstones weigh less than one carat (200 mg) and rarely exceed two carats/400 mg.
Identification of pezzottaite cat's eye
Except for hardness 8 on the Mohs scale. Physical and optical properties of pezottaite, i.e. specific gravity 3.10, refractive index 1.601-1.620. The birefringence of 0.008 to 0.011 (unrestricted negative) is higher than typical beryllium. The pezzottiat is brittle, with a broken shell to an irregular shape, with white streaks.
Like beryl, it has imperfect or light cleavage at the base. Pleochroism is moderate, pink-orange or mauve to pink-violet. The absorption spectrum of pezzottaite, when viewed with a portable direct view spectroscope, covers the band with a wavelength of 485-500 nm. Some samples show additional faint lines at 465 and 477 nm and a faint band at 550–580 nm.
Most, if not all, of Madagascar's deposits are depleted. Pezzottaite has been found in at least one other site, Afghanistan: this material was initially thought to be rich in cesium morganite/pink beryllium.
Like morganite and bixbite, pezzottaite is believed to owe its color to radiation-induced color centers, including trivalent manganese. Pezzottaite will lose color when heated to 450°C for two hours. But color can be restored using gamma rays.
Raspberry-beryllium cat-eye effect
In gemology, chatter, chatter or cat's eye effect, this is an optical reflection effect seen in some gemstones. Derived from the French "oeil de chat", meaning "cat's eye", chatting occurs either due to the fibrous structure of the material, as in cat's scale tourmaline, or due to fibrous inclusions or cavities in the stone, as in chrysoberyl.
The deposits that trigger the chat are the needles. There were no tubes or fibers in the samples tested. The needles settle perpendicular to the cat's eye effect. The needle grid parameter corresponds to only one of the three orthorhombic axes of the chrysoberyl crystal due to alignment in that direction.
The phenomenon resembles the glow of a silk coil. The luminous band of reflected light is always perpendicular to the direction of the fibers. In order for the gemstone to best show this effect, it must be in the form of a cabochon.
Round with a flat base, uncut, with fibers or fibrous structures parallel to the base of the finished stone. The best finished specimens show a sharp single. A line of light passing through a stone as it rotates.
Lower quality Chatoyant stones exhibit the striated effect typical of cat's eye varieties of quartz. Faceted stones show the effect poorly.
Cat's eye pezzottaite from Madagascar
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