ORO BLANCO DISTRICT
In the extreme west end of the county is located the Oro Blanco District
which has attracted attention through many years, and to a great extent its
history is traditional. Vestiges of many
arrastras show that it was worked for
native gold by Mexicans. It is about eighteen miles northwest
from Nogales, and the famous Planchas de Plata Mines lie about ten miles
south, in Mexico. The district extends about ten miles north from the international
line, and its greatest width is about four miles. Geologically the Oro
Blanco country is classed as "late cretaceous," yet there are intrusions of
igneous rocks, including andesite, ryolite, dacite and
quartz porphyry. The mineral belt extends in a northwesterly
direction. The chief production has been
gold, and as there runs
silver with it, giving the metal a lighter appearance than
usual, it is known as "white gold" (oro blanco) or
electrum, from which the region takes its name.
Doubtless the first work was in placer
ground, and there remain yet some good placers. During rainy seasons the
natives find in the gulches and arroyos small nuggets and bits of gold. The
presence of the ruined arrastras mentioned shows that the quartz ledges were
worked at some time, whether by the Spaniards in the antigua days, or later
by Mexicans, is a matter of conjecture. The earliest record of American
mining dates from 1865, when a man named Clinton Thompson was there working
on what is now the Austerlitz Mine.
The quartz ledges are all strong and well defined, and in some parts of the region they are close and frequent. Gold and silver ore predominate, but copper is becoming manifest. In remote geologic time some great seismic disturbance rent, shattered and pulverized the rocks in all directions, and the interstices offered precipitation surfaces for the vaporous solutions rising from the depths, which, cooling, precipitated and converted into the metallic ores that are found. Near the international line there is a deposit of granite. In the southeastern part of the district there have been found extensive beds of potassium and potash. Oil-bearing shale is in evidence also. It is found near the camp of the Progressive Mining Company, springs of water showing oil float upon their surfaces. Whether the shale is an anticline or syncline has not been investigated. But if it is ever found to be a syncline, boring to the bend of the up tilted strata would produce oil, in paying quantities probably.
The principal mined of the area are the Austerlitz, Switzerland, Ragnaros, Oro, Old Glory, Oro Blanco, Tres Amigos, Triangle, Warsaw, Franco-American, Grubstake, Yellow Jacket, Montana, Portland, etc. In some of them are extensive development with exposure of large and valuable ore bodies. In the early history of recent operations, thirty years ago or more, there were erected several quartz mills, but the processes seemed poorly adapted to the character of the ores, and they fell short in saving the values. All can be made to pay handsomely by installation of more modern and efficient extraction processes. The Oro Blanco Mine is said to have blocked out and ready for stoping many thousand tons of gold ore that can be made to pay well. Its owner is a banker in Scranton, Pennsylvania. The Old Glory shows above ground on one side a great gold-bearing ledge that is exposed to a height of 100 feet and a length of several hundred. From the ledge, which is about forty feet in width, gold-bearing rock has been quarried and sent down to the mill below. The mine has also considerable underground development.
AUSTERLITZ MINE
The Austerlitz has been a good producer, and it gives evidence of the making
of a great mine. In 1912 Woodworth & Lane, who were working under bond and
lease, shipped to El Paso and Pioneer smelters 1,414.5 dry tons of ore, and
180.4 dry tons of concentrates, for which they were paid $57,223.44. The
Austerlitz and adjacent claims show on the surface an oxidized ore zone the
ores from which average well in gold and silver, and often run to high
grade. At greater depth there is penetrated a sulfide zone, the rock in
which is extensive, massive and frequently high-grade, running well in
silver, gold and copper. The deep-seated rocks are andesite, with an
overflow of
rhyolite. It is predicted that were the rhyolite cut through there
would be found a great body of sulfide
copper ores, rich in gold and silver. The Austerlitz is owned by
Doctor A. H. Noon, of Nogales, but at this writing it has been taken over
under bond and lease by Mr. Camphaus, an English mining operator.
In the extreme northwest corner of the Oro Blanco District is the Yellow Jacket mine, a gold producing property with a 10-stamp mill. It has lain idle twenty-one years, but recently work has been resumed by Mr. W. N. Gourley, of Philadelphia, whose deceased father's estate holds the title. The foregoing pages serve to give some idea of the mines and mineral resources of Santa Cruz County. They are great and inexhaustible. To appreciate them investigation is necessary, which is invited.
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