Prof.
Miers has shewn that when a mixture of red-lead and flowers of sulphur
is sprinkled, through a muslin sieve, on to a Tourmaline which having
been warmed is slowly cooling, the orange powder is at once separated
into its components ; the red-lead, becoming positively electrified by
friction through the sieve, flies to the negative end of the
Tourmaline, whilst the sulphur being negatively electrified, attaches
itself to the positive end.
Tourmaline
is found in Siberia, Ceylon, the Urals, Burma, Saxony, and the Isle of
Elba. In the United States, it has been discovered in great perfection
and abundance, especially at Mount Mica, Paris, Maine.
The
Siberian Tourmaline is of carmine hyacinth, purple, or rose-red,
running into violet-blue. When polished its lustre somewhat resembles
that of the Ruby, and the mineral is sometimes known as " Siberian
Ruby."
The
Green Tourmaline generally occurs of an olive or dark green colour, and
takes a perfect polish. Crystals of great beauty are found in
Minas-Geraes. The Yellowish-Green Tourmaline, " Ceylon Chrysolite," is
very like an Aquamarine, and is found in the river beds of Ceylon and
Brazil. Colourless Tourmaline occurs very seldom in pieces worth the
cost of cutting and polishing. Brown and Black Tourmaline are varieties
not used for purposes of ornament. Black Tourmaline or Schorl is by no
means uncommon in this country, especially in the tin-bearing districts
of Cornwall.
The
value of Tourmaline depends upon the colour, quality, and size of the
specimens ; one of exceptional colour and purity, of five carats
weight, might be worth about £20, but others only a few shillings.
