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PRECIOUS STONES
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135
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CHRYSOBERYL
The name is derived from the Greek chrysos, golden, and beryllos, beryl.
Alexandrite
and Oriental cat's-eye are varieties of this stone. It is found in
Ceylon, Borneo, Brazil, Europe, and the United States.
Crystallization trimetric. It occurs in double six-sided pyramids; often found as rolled pieces.
Hardness, 8.5; specific gravity, 3.5 to 3.8.
Lustre vitreous to resinous; transparent to translucent.
Cleavage imperfect; fracture conchoidal.
Doubly
refractive (index, 1.756 and 1.747); dichroic; twin colors of yellow,
golden brown and greenish yellow; positively electric by friction,
lasting several hours.
It
is composed of alumina, 78 to 79; glucina, 18 to 20; and a small
percentage of oxide of iron. In the alexandrite less iron and a very
small quantity of chrome.
Infusible and unaltered before the blow-pipe; it is not subject to acids, but melts with borax or salts of phosphorus.
Color, light golden yellow to brown and green; sage and leaf-green; very similar in some colors to the chrysolite.
The light golden yellow was valued nearly as high as the diamond in the time of Louis XIV.
Cut step and brilliant.
The cymophane (from kyma, wave, and phaino, to appear) is a somewhat milky variety of the chrysoberyl, which shows a floating spot of light as it is moved. It is cut en " cabochon, like the cat's-eye.
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