Amatrice
is especially adapted for jewelry where matrix stones are desired. It
has bright colors of its own, and does not resemble the green seen in
discolored turquoise matrix. The variety of combinations of matrix and
colors is probably greater than that found in turquoise, and the rich
green of amatrice is more attractive in certain classes of jewelry
than the blue of turquoise. The gems are generally cut in rounded or
cabochon forms and are used in rings, scarf pins, brooches, necklaces,
pendants, etc. Amatrice is becoming popular and the Occidental Gem
Corporation reports a production of about 45,000 carats during 1908.
The gems are retailed at $1 to $3 a carat.
Utahlite.—The
utahlite or chlorutahlite mine is in Clay Canyon, 1-1/2 miles west of
Fairfield, Utah County, at the south end of the Oquirrh Mountains. It
is operated intermittently whenever a new supply of gem material is
needed. The deposit is located at the foot of the hill on the north
side of the canyon, a few feet above the bottom. The walls of the
canyon, or more properly valley, are not steep at this point.
Development consists of a tunnel 110 feet long, driven nearly north
into the hill, and an open cut with a small incline. The tunnel did not
cut the variscite lead. The country rock exposed in the workings is
black limestone, which strikes about N. 50° W., with a dip of 22° N.
The variscite lead has a steeper dip to the north, nearly 45°, with
approximately the same strike as the limestone. The variscite occurs in
concretionary nodules in a brecciated, more or less decomposed, zone.
Practically everything in this zone has a nodular shape, including the
blocks of limestone breccia, etc. Chert forms a prominent part of the
filling of the mineralized zone and has been fractured and cemented by
calcite seams and limonite stains. The nodules of variscite range from
one-fourth of an inch to over 4 inches in thickness. The nodules have
been more or less fractured, and the cracks have been filled in with
yellow and white phosphate minerals. Some of the larger nodules contain
two or more smaller nodules or irregular masses of variscite, inclosed
in yellow and white matrix or shells. Most of the nodules are
surrounded by banded layers of the yellow phosphate and some have white
coatings also. The colors of the variscite range from deep grass or
emerald green to paler shades and nearly white. The deeper colors show
a tendency to appear near the borders of the nodules. Some of the
variscite nodules yield large pure gems of beautiful color. Others
furnish handsome matrix stones, though the number of variations of
pattern and the contrasts of colors occurring in small areas are not
so great as in amatrice. Some of the yellow phosphate mineral, with or
without thewhite in seams through the massive variscite, furnishes
exceedingly attractive gems.
The
nodular and brecciated chalcedony and phosphate minerals associated
with variscite at both the amatrice and utahlite mines would furnish
handsome material for small ornaments of mosaic work, even where there
is no green variscite present. The concretionary and agate-like
structure of the nodules and the massive matrix with small nodules
throughout give odd patterns and effects. Where the colors are marked,
as in much of the yellow phosphate mineral and chalcedony the matrix
could even be used for gem purposes.
