directions,
the larger veinlets often having stringers extending out in seams
crossing them. The joints and seams in the vicinity of
turquoise-bearing ground often show indications of turquoise in the
form of blue, bluish-green, green, yellowish-green, and whitish
coatings or stains.
Choice
lots of turquoise that range from deep robin's-egg blue to blue of pale
shades and that would yield one color gems of 10 to 20 carats (or even
of 30 carats) are reported to have been obtained from this mine. The
largest yield of turquoise of one color is in stones of 1 to 10 carats,
while considerable matrix material and mottled turquoise are reported
to have been found. Mottled turquoise presents a number of variations
of light-blue turquoise speckled with dots of deeper blue. In one
specimen seen the dark blue mottling consisted of small dendritic
masses resembling the markings in moss agate. Judge M. M. Porterfield,
owner of the mine, states that the deep-blue stones of finest quality
when cut bring from $1 to $10 per carat for those under 10 carats in
weight and $10 or more per carat for those weighing over 10 carats. The
matrix stones bring from 25 cents to $1 per carat, and the mottled
turquoise brings a little more than the matrix. The Porterfield
turquoise when cut is marked with a cross (x) on the lower side, as are
those of the American Gem and Turquoise Company. With better facilities
for marketing, the production of the Porterfield mine could probably be
considerably increased.
UTAHLITE AND AMATRICE OR VARISCITE MATRIX.
Amatrice
is the new name given to utahlite or variscite with its associated
matrix, as now mined and cut by the Occidental Gem Corporation of Salt
Lake City. The word "amatrice" is a combination of the first letter of
the word American and of the word matrice, and is intended to indicate
that the gem is a matrix stone of distinctly American origin. During
1907 the Occidental Gem Corporation worked the deposit of utahlite in
the Stansbury Mountains, Tooele County, Utah, described by Dr. George
F. Kunz in this report for 1905. The company reports about 100 feet of
tunnel opened and 30 feet of cuts made. The gem occurs in nodular form
with a coating of chalcedony and other minerals. The production of
finished gems from the rough material mined amounted to about 20,000
carats.
Amatrice
is composed of variscite, wardite, and probably other allied minerals,
chalcedony, and quartz. Variscite and wardite occur together and both
are hydrous phosphates of aluminum with colors ranging from deep grass
green to paler shades of green and slightly bluish green. Both minerals
are compact and tough, the hardness varying from a little over 4 in
variscite to about 5 in wardite. The matrix consists of chalcedony and
quartz with other minerals, among which are yellowish gray and white
phosphates, probably in part variscite or allied minerals, sometimes
deposited around portions of green variscite or banded with chalcedony.
In both the variscite or wardite and the adjoining matrix there is an
oolitic texture with the shot-like masses recemented together with
mineral of a different shade of color. Much of the chaledony is dull
and chert-like, with the color varying from dark red and yellow brown
to buff and gray.
The
charm of amatrice is due to the wide range of colors of the several
minerals composing it and the numerous combinations these colors make
with one another. These combinations of color are due
