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Emeralds 65
resulted
in: silica, 66.17; alumina, 20.39; beryllia, 11.50; ferrous oxide,
0.69; soda, 0.24; water, 1.14, and a trace of lithia.
The
only acid which will attack beryl, so far as has been discovered, is
hydrofluoric acid. Before the blowpipe beryl becomes white, cloudy, and
fuses, but only with difficulty, at the edges to a white blebby glass.
Beryl,
like all other hexagonal crystals, is bi-refringent, but only to a
small extent. The beauty of beryl, therefore, depends not upon a play
of prismatic colours, but upon unusually strong lustre and a fine
body-colour. The bright grass-green beryl is the emerald; the pale
varieties are styled precious or noble beryl. Aquamarine is pale-blue,
bluish-green, or yellowish-blue; the yellowish-green variety is called
aquamarine-chrysolite; jewellers call the yellow variety beryl and the
pure golden-yellow golden beryl. The dichroism of all transparent
varieties of beryl can often be discerned with the eye unaided by the
dichroiscope; this property usually suffices to clearly distinguish
beryl from any imitations. A curious characteristic °f the emerald
beryl is that its colour is by no weans always uniformly distributed
through the body of the stone; the different coloured por-
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