emerald
- green colour, or sometimes colourless. The emerald-green form
contains chromium. It has a high lustre, almost adamantine; the
refractive index is greater than in most Garnets, and the dispersion
much more marked, hence there is some play of colour in a cut
specimen. It occurs in transparent masses, rarely in crystals. It is
softer than the other Garnets, being only equal to 6-1/2. The mineral
is more easily attacked by acids than other members of the group, but
it is very infusible. It is found in the Ural Mountains (and so is
sometimes called Uralian Emerald) at Nizhni Tagilsk in gold washings,
and in situ in serpentine in the Sissersk district.
Topazolite, another variety of Andradite, is found at Ala in Piedmont; in colour it is a yellow inclining to green.
Melanite,
a common black form of Andradite (Fig. 25), occurs at Frascati near
Rome and in Baden. It is used sometimes in mourning jewellery.
Uvaeorite, a
Garnet of brilliant emerald-green colour containing chromium, is found
in the Urals in cavities in Chromic Iron ; unfortunately the specimens
are too small to use as gems.
Rhodolite,
so called from the similarity of its colour to that of the
rhododendron—a light red—is a Garnet found at the Corvee Creek Corundum
mines in Macon County in North Carolina, United States. It has a very
high lustre and a freedom from flaws which makes it very valuable as a
gem. In composition it is intermediate between Pyrope and Almandine.
Garnet
is largely used as an abrasive, often being made into garnet-paper
similar to glass- and sand-paper. Many of the pivot bearings of good
watches are made of Garnet
