The Hardscrabble mining district, in which both Silver Cliff and Rosita are situated, takes its name from a small creek that rises in the foothills on the west side of the Wet Mountain range, or Sierra Mojada, and, forcing its way through a wild and difficult cañon, flows into the Arkansas river seven or eight miles east of Cañon City. The mountains themselves are of red granite, which has been thrown up in the wildest confusion, and which the winds and rains in many places have carved into all sorts of fantastic shapes. The range is extremely rugged, almost destitute of large timber, and is impassable for wagons, except where roads have been built at great expense through the cañons and over the divide.
The western foothills of the Sierra Mojada generally present, at a distance, a smooth, rounded appearance, with now and then a ledge of rocks sticking out of the summit or side, and while on some of them timber of considerable size is growing, in most instances the vegetation consists solely of a few stunted evergreen bushes and a very thin growth of gramma grass. The soil on these hills is generally very thin, and, on approaching them, the surface is found to be covered with loose pieces of broken rock, which the frosts have detached and the rains washed out from beneath a slight covering of earth. It is in these foothills that all the best mines of the Hardscrabble district have been found.
The geological formation of this rich mineral belt is peculiar and very interesting. Resting upon and against the granite of the Wet Mountain range and its higher foothills, and extending down into the valley beyond the southern line of the belt, lies an enormous deposit of porphyry, or trachyte, a volcanic rock poured out and consolidated during the tertiary period. Its width is at least five miles, and its length is probably fifteen or twenty. Extending into the trachyte formation from the southwest, and following its general direction, is a tongue-shaped mass of granite about three-fourths of a mile wide and at least seven or eight miles long. When the trachyte was poured out this granite apparently formed a ridge which rose above the level of the fluid mass of the surrounding volcanic rock, and therefore was not covered by it. That it does not now stand higher than the surrounding country does not disprove this theory, because there are everywhere to be found evidences of terrible convulsions since the trachyte was deposited which have completely changed the face of this entire region. The mines here are found both in the granite and also in the trachyte. Winding through the porphyry, in a serpentine course, there is also a stream of obsidian, as it is called here, or volcanic glass, mixed with trachyte and quartz bowlders. This stream, where it has been examined, varies from a few feet to many rods in width, and in crevices of the bowlders which form the mass of it were found, on the Hecla claim, some very rich specimens of horn silver.
At Silver Cliff, and north of there especially, the trachyte rock has been shaken up and fractured in all directions, and in many places the crevices have been filled with iron and manganese, which has become oxidized, and with chloride of silver. This is the free milling ore which is found in all the mines that lie directly north of this town and adjoining it. The trachyte is of itself yellowish white; when it is stained with the black oxide of manganese and the red oxide of iron that variegates the ores, it is sure to carry silver, though this (in the form of a chloride) can rarely be seen. Sometimes, however, the silver can be seen upon the surface of a fracture in the form of a green scale, or appears in little globules of horn silver. While the rich ore is discovered in large masses, surrounded by leaner or less valuable rock, there is nowhere in the chloride belt anything that looks like a vein. The rock just covers the entire face of the country over an area two miles long and half a mile wide, and the whole mass of it contains at least a small quantity of silver.
The theory of the geologists, accepted by the miners, is, that the trachyte, after it became solidified, was shaken and broken up by some great convulsion, and that simultaneously, or afterward, silver, iron, manganese, and the other metals of which traces are found in the rock, were disseminated through crevices, either in water solutions or volatilized—in the form of gases. These solutions or gases are supposed to have come up through cracks in the earth’s crust. Such a deposit is called in the old world “stockwork,” and Professor J. S. Newberry, in writing recently of “The Origin and Classification of Ore Deposits,” mentions this as one of the two most important examples of this kind of deposit that have come under his observation. The other is the gold deposit in Bingham cañon, Utah. None of the oldest miners ever saw before any ore that looked like this at Silver Cliff, and this explains their failure to discover its value until recently. The same is true of the quartzite gold ore in Bingham cañon. The miners worked for years there getting out silver-lead ores, but threw aside the gold ore as waste, not dreaming of its value.
THE ROYAL GORGE
But the mineral belt which I have described contains other classes of mines. At Rosita, in the “Pocahontas-Humboldt” lode, the trachyte, instead of being shattered and impregnated, has been rent asunder and a true fissure formed in it, filled with gray copper, galena, zinc blende, iron and copper pyrites and heavy spar—all carrying sulphide of silver. These form a narrow pay streak from one to eighteen inches wide, and the remainder is filled with a gangue rock, generally of a trachytic formation. This vein extends for a long distance through the hills, and is inclosed by walls that are as clearly defined as those of a room. Other smaller veins of the same character have been found in the country north of Rosita, and on some of them valuable mines have been located and developed.