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A cameo is not a gem itself. It is a form of carving or engraving a stone or other material in a raised low relief. (See Chapter 3.) If the cameo is stone, such as layered jasper, it has the same qualities as that stone.
If it is shell, as Italian cameos are, it has t same qualities as shell. The larger the cameo and the greater detail, the more desirable and expensive it is.
Shell cameos are reasonably tough, despite being soft. Although they tend to scratch, with reasonable care they are durable. They a not durable, however, in the sense that gemstones are. Cameos tendto disintegrate over a long period of time, but cameos several hudred years old are found in museums. Thus, a cameo from "Romatimes," when cameos were popular, is an impossibility. Such she cameos have to be fake.
CHRYSOBERYL
Chrysoberyl, which is 8'/s on the Mohs scale, is very hard, ranking third after diamond and corundum in hardness. It has no distinct cleavage and is brittle, with a limited color range. Transparent chrysoberyl ranges from yellow and brown to blue-green and Translucent chrysoberyl is called cat's-eye chrysoberyl and is w d for its chatoyancy and cat's-eyes. Although rare and highly 1able to collectors, chrysoberyl is relatively unknown except for the cat's-eye variety.
Alexandrite
A relatively new discovery, alexandrite is rare and extremely expensive is dichroic, showing two colors depending on the light. It was discovered in the Russian Urals in the 1830s. Miners looking for emeralds found some gems that looked like emeralds, that is, until they look them back to camp.
There, they noticed that in firelight the stones turned red. The mysterious gem was named alexandrite in r of the heir apparent to the Russian throne, who later became Alexander II. It became popular in Russia because its colors-red green-were the colors of Imperial Russia. The stone is also : in Ceylon, where the stones are less emerald in color and are a browner red.
