of 1,680 carats weight, and called the Braganza, is probably a topaz of exceptional clearness and beauty.
The
Brazilian topazes come mostly from the province of Minas G-eraes. While
those of greenish and bluish shades are found mostly in the form of
rolled pebbles, the yellow Brazilian topaz is found in the mother rock.
This is a decomposed itacolumite, of a white or yellow color. The
principal locality is near Ouro Preto.
-The
Russian topazes like that shown in the colored plate, come from the
Imperial mines in the Urals. Alabashka, near Mursinka, is one of the
most productive localities. The crystals occur in cavities, in
granite, and are accompanied by crystallized smoky quartz, feldspar,
and mica. Superb gems are cut from these topazes, a fine series of
which is possessed in this country by the Field Columbian Museum and
the United States National Museum. The Russian mines are owned and
operated by the Russian Government, and the finest specimens are
reserved for the Imperial Cabinet.' In the southern Urals, in the gold
washings of the River Sanarka, yellow topazes are found closely
resembling those of Brazil. Associated with them are amethysts, rubies,
chrysoberyls, and many other precious stones./^Topaz crystals of good
size and color are found quite abundantly in Japan, although they have
not yet been cut for gems to any extent. There are many localities in
the United States where topaz occurs, and it is often of gem quality.
The group shown in the plate illustrates the occurrence of topaz at
Thomas Mountain, Utah, a locality forty miles north of Sevier Lake.
These crystals are found in cavities in the rock. They are never very
large, but are usually clear and bright. They occur in somewhat similar
fashion at Nathrop, Colorado. In the Eastern States topaz was first
found at Trumbull, Connecticut. It is here quite opaque, and not
suitable for gem purposes. Good gem topaz has been found at Huntington
and Middletown, Connecticut, however, and at North Chatham, New
Hampshire. In these localities it occurs in pegmatitic granite.
Of
other stones which are sold under the name of topaz, the most common is
the so-called Spanish or Saxon topaz. This is simply smoky quartz,
heated until it turns a yellow color. It can easily be distinguished
from true topaz by the properties of the latter above given.
At
the present time it is also quite a common practice to vend ordinary
colorless quartz under the name of topaz. These practices are harmful
to the reputation of true topaz, as these forms of quartz lack several
of the desirable qualities of that stone. The so-called Oriental topaz
is a yellow form of corundum. It is heavier and harder
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