chrysoberyl


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chrysoberyl

(krĭs`əbĕr'ĭl) [Gr.,=golden beryl], a beryllium aluminate used as a gem. It has a vitreous luster and is transparent to translucent. The more valuable cat's-eyecat's-eye,
gemstone that displays a thin band of reflected light on its surface when cut as a cabochon. Its name is derived from its supposed resemblance to the eye of a cat.
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 is a variety of chrysoberyl. Another variety, alexandrite, was first discovered in the Ural Mts. of Russia, on the birthday of Czar Alexander II, for whom it was named. It is remarkable in that it is green by daylight and raspberry red under artificial light. It was popular in imperial Russia, both because of its association with the czar and because red and green were the colors of the empire. It is now found chiefly in Sri Lanka and Brazil.

Chrysoberyl

 

a mineral of the subclass of multiple oxides, with the composition BeAl2O4. Chrysoberyl crystallizes in the orthorhombic system. Small short-columnar crystals are common, and tabular crystals sometimes occur. Flattened twins and triplets are typical. The color is yellowish or yellowish green. The emerald-green, chromium-containing variety of chrysoberyl that appears red-violet in artificial light is called alexandrite (seeALEXANDRITE); the golden yellow variety exhibiting a bluish chatoyancy is called cymophane, or cat’s-eye. Chrysoberyl has a vitreous luster, a hardness of 8.5 on Mohs’ scale, and a density of 3,500–3,700 kg/m3.

Chrysoberyl is found in the form of large segregations together with muscovite and beryl in granitic pegmatites occurring in rocks with a high aluminum content. It is typical of beryl-bearing magnetite-containing skarns. It is associated with taaffeite and spinel in magnesian skarns. Chrysoberyl is also typical of fluoritic metasomatites. Alluvial deposits are found in Burma and Sri Lanka. Fluoritic metasomatites with chrysoberyl and phenakite that have a high BeO content may serve as beryllium ores. Translucent chrysoberyls with attractive colors, that is, alexandrite and cymophane, are gems of order, or class, I.

REFERENCES

Mineraly: Spravochnik, vol. 2, fasc. 3. Moscow, 1967.
Geneticheskie tipy gidrotermal’nykh mestorozhdenii berilliia. Moscow, 1975.

A. I. GINZBURG

chrysoberyl

[′kris·ə‚ber·əl]
(mineralogy)
BeAl2O4 A pale green, yellow, or brown mineral that crystallizes in the orthorhombic system and is found most commonly in pegmatite dikes; used as a gem. Also known as chrysopal; gold beryl.

chrysoberyl

guards against evil spirits. [Gem Symbolism: Kunz, 65]
References in periodicals archive ?
Figure 1 shows four examples of cat's-eye stones, consisting of two chrysoberyls (left) and two sillimanites (right).
And the Natural History Museum of London brought over a single "historic" gem: the "Hope" chrysoberyl, a brilliant yellow-green fancy-cut stone of 44 carats fashioned in ca.
Luis also had dozens of small specimens showing chrysoberyl as sharp, pale green, V-twinned crystals to 2 cm lying flat on the cleavage surfaces of sharp, diamond-shaped muscovite crystals, these from the Ipiau, Bahia, where they were found last December.
apatite, aquamarine, ashanite, bimushite, bismutomicrolite, chrysoberyl, *cygrayite, epidote, ertixiite, fluorite, garnet, hiddenite, holmquistite, ilmenite, ishikawaite, manganotantalite, manganocolumbite, molybdenite, muscovite, phenakite, pollucite, polylithionite, pyrite, *qingheite, samarskite, scheelite, sphalerite, spodumene, staurolite, topaz, tourmaline, trilithionite, uraninite, zircon Labashan Hubei turquoise Laiyuan Hebei hematite, ludwigite Lamo Guangxi, apatite, galena, pyrite, quartz, Zhuang A.
Excellent" milarite specimens were collected here in the late 1960's (White, 1970); at around this time the Smithsonian acquired fifty fine specimens which a dealer had offered as chrysoberyl.
Other associated minerals are: dravite-uvite series, chrysoberyl, phlogopite, magnesiohornblende-edenite series, cordierite, phenakite, clinochlore, and others.
Another specimen that qualifies as really big was the 54-pound, 122,400-carat uncut chrysoberyl twin exhibited by the Amsterdam Sauer Company.
All the specimens were Russian classics like topaz, aquamarine, exceptional chrysoberyl and the like.
Box 12027, Vorna Valley, 1686 Republic of South Africa), one saw nice, newly mined examples of the loose, cyclic-twinned alexandrite chrysoberyl crystals which have long been found intermittently in prospects around Fort Victoria (British colonial-em name), now Misvingo, in Zimbabwe.
Of special interest were two cases of "rarities" from Colorado; it is indeed rare, and of course educational, to see fine Colorado specimens of, for example, allanite, bismuthinite, chrysoberyl, chlorargyrite, and phosgenite.