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698 MINERAL RESOURCES.
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rock,
this ought to find a market as a high-class ornamental stone. It is
mistaken here for lapis lazuli. The locality where this dumortierite
occurs can be worked only in the winter or in the rainy season, as the
water has to be hauled from the Colorado river, and the climate is too
hot from June until December for horses or white men in that locality.
OPAl.
Opals
were discovered in Idaho during the summer of 1892 by Mr. George
Shirley, Mr. P. B. Schermerhorn, and Mr. H. C. Anchor, who kindly
furnished me with the following information.
The
Owyhee opal mines of Idaho are situated on section 13, township 1
north, range 4 west, Boise meridian, about 3 miles from Snake river in
Owyhee county. The work done on the mine amounted to about eight
months' work for two men. The opal taken out amounted to about 7,000
carats in the rough, varying from transparent fire opal to the finest
white noble opal; but nearly all that they found was given away or
poorly marketed. They are found in a dike or vein of dark blue or black
andesite rock, 25 feet in thickness, running in a northwest and
southeast direction with a nearly perpendicular pitch. This crops out
on the surface for a distance'of about 750 feet in length by 25 feet
wide. In the center of this dike is a stratum of jasper, very hard, 4
to 5 feet wide, on each side of which the opals are found in seams and
flat pockets. Opals have been traced for a distance of 250 feet along
the surface. The greatest depth reached is about 20 feet, all open cuts.
North
of and parallel with this dike is a smaller dike traced for about 50
feet in length, by 8 feet in width. It has produced about 1,000 carats
of good stones.
The
North America Gem and Opal Mining Company, which works the mines at
Moscow, Idaho, did no work during the year 1893, owing to a litigation
with a former owner* but it is believed that in 1894 active operations
will be carried on.
Opals
were announced as having been discovered on a school section in Lincoln
county, Washington, and a committee was appointed to investigate and
report upon the discovery. It proved not to be a genuine find.
During
the past two years opals have been found at Wilcannia, New South Wales,
which in quality are quite equal to those from the famous Hungarian
mines. It is reported that about 500 men are already on the fields and
an immense amount of work and prospecting is going on. The opals found
here are generally free from the yellow tint which the Queensland
stones show by transmitted light. They are found in a fossiliferous
sandstone rock. Many of the fossil univalve and bivalve shells are
entirely changed to a beautiful noble opal, as is also the case with
wood and branches of trees found in the same district. Some fine stones
weighing nearly 50 carats each have been obtained at this place.
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