EMERALD

( Emeraude , Fr.; Smaragd , Germ.) Is a precious stone of a beautiful green colour; valued next to diamond, and in the same rank as oriental ruby and sapphire. It occurs in prisms with a regular hexagonal base; sp. grav. 2·7; scratches quartz with difficulty; is scratched by topaz; fusible at the blowpipe into a frothy bead; the precipitate afforded by ammonia, from its solution, is soluble, in a great measure, in carbonate of ammonia. Its analysis is given very variously by different chemists. It contains about 14 per cent. of glucina, which is its characteristic constituent; along with 68 of silica, 16 of alumina, a very little lime and iron. The beautiful emerald of Peru is found in a clay schist mixed with some calcareous matter. A stone of 4 grains weight is said to be worth from 4 l. to 5 l. ; one of 8 grains, 10 l. ; one of 15 grains, being fine, is worth 60 l. ; one of 24 grains fetched, at the sale of M. de Drée’s cabinet, 2400 francs, or nearly 100 l. The beryl is analogous in composition to the emerald, and is employed (when of the common opaque kind, found near Limoges,) by chemists, for procuring the earth glucina .