It
will be observed that the emerald has more glucina than the beryl; and
chemists find that the greater the quantity of glucina there is in a
specimen, the greener is the crystal.
Before
the blowpipe, the emerald remains unchanged —sometimes, however,
becoming a little cloudy; with borax it fuses into a pale green
substance not very unlike glass. It is not afFected by acids, but is
slowly soluble with microsmic salt (or salt of phosphorus).
Formerly
it was supposed that the colouring matter of the emerald was the oxide
of chrome, but the quantity of chromic acid obtained by Mr. Lewy on
k 2
