l solution
of violets, of which a drop only need be taken for test, is turned green
by adding to it a few grains of topaz dust, or of a little splinter
crushed to fine powder.

_The Beryl._

The beryl is a compound of silicates of beryllia and alumina, with the
formula 3BeOSiO_{2} + Al_{2}O_{3},3SiO_{2}, or
3BeO,Al_{2}O_{3},6SiO_{2}. It differs very little indeed from the
emerald, with the exception of its colour. In the ordinary varieties
this is somewhat poor, being mostly blue, or a dirty or a greenish
yellow; the better kinds, however, possess magnificent colour and
variety, such as in the aquamarine, emerald, etc. The cleavage is
parallel to the basal plane. Its lustre is sometimes resinous, sometimes
vitreous, and it crystallises in the 2nd (hexagonal) system. It occurs
in somewhat long, hexagonal prisms, with smooth, truncated planes, and
is often found in granite and the silt brought down by rivers from
granite, gneiss, and similar rocks. It is found in Great Britain and in
many parts of Europe, Asia, and America, in crystals of all sizes, from
small to the weight of several tons. The common kinds are too opaque and
colourless to be used as gems and are somewhat difficult of fusion under
the blowpipe, on the application of which heat some stones lose their
colour altogether, others partly; others, which before heating were
somewhat transparent, become clouded and opaque; others suffer no change
in colour, whilst some are improved. In almost every case a slight
fusion is seen on the sharp edges of fractures, which become smooth,
lose their sharpness, and have the appearance of partly fused glass.
The hardness varies from 7-1/4 to 8, the crystals being very brittle,
breaking with a fracture of great unevenness. The better varieties are
transparent, varying from that to translucent, and are called the
"noble" beryls. Transparent beryl crystals are used by fortune-tellers
as "gazing stones," in which they claim to see visions of future events.

_The Emerald._

Considering the particular emerald which is a variety of beryl--although
the name emerald in the trade is applied somewhat loosely to any stone
which is of the same colour, or approaching the colour of the beryl
variety--this emerald only differs chemically from the beryl, just
described, in possessing an addition of oxide of chromium. In shape,
crystallisation, fracture and hardness, it is the same, and often
contains, in addition to the chromium, th