Chrysoberyl has rarely, if ever, been found in situ, but
the secondary deposits in which it occurs are so constantly those
derived from the weathering of granite and gneissose rocks that there
is little doubt it is in such rocks that it has its origin. The
principal locality for Chrysoberyl of the ordinary variety is the state
of Minas Geraes in Brazil, where it is met with sometimes in
association with Diamond. More often the associates are, Quartz and its
varieties, Tourmaline, Euclase, Topaz, Garnet, and Spinel. In
ConÂnecticut, at Haddam, it occurs with Tourmaline, Garnet, and Beryl,
in granitic bands in gneiss. In Moravia it is found at Marschendorf. An
important locality is in the Ural Mountains, about sixty miles east of
Ekaterinburg, associated with Topaz and Euclase. Here the variety
Alexandrite is found, with Emerald, in mica-schist close to granite.
Alexandrite was named after Alexander II. of Bussia. More recently it
has been found in the southern Urals. Much of the Chrysoberyl that is
suitable for gem use is found in Ceylon in the gem gravels in rolled
pieces. Here all three forms are found, the ordinary variety of
different tints of green, the chatoyant variety Cymophane, and
Alexandrite. The Cymophane is known sometimes as Ceylon Cat's Eye or
Oriental Cat's Eye, to distinguish it from the Quartz Cat's Eye.
In chemical composition Chrysoberyl is beryllium aluminate BeO, A1203.
The ordinary variety contains iron usually, and the variety Alexandrite
is supposed to owe its colour to traces of chromium oxide.
Chrysoberyl
is one of the minerals used as pivot bearings in watches and
chronometers. Its use in jewellery is much subject to the fashion of
the moment, and the demand
