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MINERAL RESOURCES.
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NORWAY.
Dr. E. S. Ward, of Rochester, N. Y., reports several hundred pounds of thulite imported from Norway for gem purposes.
TOPAZ.
UTAH.
The
following notes on the occurrence of topaz in the Thomas Range, Utah,
have been abstracted from an article by Horace B. Patton.a
This occurrence of topaz was first discovered by Henry Engelmann,
geologist of an expedition across the Great Basin of Utah in 1859.
Little was heard of the locality or of the topaz crystals after this,
however, until a trip was made to the region and numerous specimens
were collected in 1884 by Prof. J. E. Clavton, of Salt Lake City. Since
that time numerous collectors have visited the locality and brief
descriptions of the occurrence and crystals have been written.
The
topaz is found in the "Thomas Range" of mountains about 40 miles north of
Sevier Lake, Utah and a little over 40 miles northwest of Deseret. Locally
the mountains are called the Dugway Range, and the topaz locality Topaz
Mountain. Topaz Mountain is 8 miles northwest of Joy, Juab County. The
"Thomas Range" at the point consists of a much dissected table-land whose
southeast face rises precipitously some 1,000 to 1,200 feet above its
base for a distance of 4 or 5 miles. The part called "Topaz Mountain" is
that portion along the southeast side where topaz crystals have been
found most abundantly.
The
rocks of this portion of the "Thomas Range" are of volcanic origin and
rest on sedimentary formations of undetermined age, The only
sedimentary rock exposed near the topaz locality is a bluish-gray
limestone. Above this, in order, are rhyolite tuffs and lava flows,
andesitic at the base, with several hundred feet of the more acidic
rhyolite above. The later rhyolite flows compose the bulk of the
volcanic rocks, and the latest of these contain the most topaz. The
rhyolite varies in color from white to light brown or brownish gray. It
shows no trace of glass and is apparently not porphyritic. In places it
is massive; in other places flow structure is marked. Macroscopically
the rock appears to be somewhat kaolinized, though under the microscope
the feldspars are seen to be very little altered. The microscopic
characters indicate a devitrified glassy lava. Litho-physaeb occur
in varying quantity through the rock, and are more abundant in certain
portions where flow structure is but little developed or absent. They
are also more plentiful in light-colored rhyolite with an evident
crystalline texture than in the darker and more dense portions. In
quarrying, fine specimens of lithophysse with numerous crystal-lined
concentric shells are obtained. The crystals on these shells are quartz
and sanadine. On weathering under desert conditions the rock
disintegrates to sand, which is swept away by
a
Topaz-bearing rhyolite of the Thomas Range, Utah: Dull. Geo!. Soe.
America, vol. 19,1908, pp. 177-192 b Lithophysas (stone bubbles) are
cellular cavities in acidic, glassy, or finely crystalline lavas. They
consist of concentric shells of crystalline material grouped about a
cavity or core. The layers are composed of crystals of such minerals as
quartz, tridymite, feldspar, topaz; garnet, etc. In cross
section the shells may present an appearance somewhat like the petals
of a partly opened rose. In diameter, lithophysae range from a fraction
of an inch to an inch or two.
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