History of the big bonanza

by Dan De Quille

When the rocks were rent apart, fragments from the edges of the chasm—principally from the east or propylite side, the side reared up—fell into the opening, and sliding down the smooth slope of the syenite, blocked the fissure, preventing its closing. Some of these fragments were at least one thousand feet long and from three to four hundred feet in thickness, and many of them were from fifty to one hundred and fifty feet in length, with a proportionate thickness. These still rest in the vein, the ore, quartz, etc. having formed about them.

By the miners these are called “horses.” They are generally composed of propylite (commonly spoken of as porphyry in the mines, owing to its inclosing crystals of feldspar and fragments of hornblende), but there are some that came from the west side of the fissure and are syenite.

After the fissure was thus propped open, still other fragments of propylite fell from its roof during the time the vein was filling with its present precious contents, and these are found to be surrounded on all sides by ore of the richest character. The cavities caused by their displacement were also filled with quartz and ore. This makes the east wall or propylite side of the vein very jagged and uneven, while the less disturbed west or syenite wall is quite regular, descending to the eastward at an angle of from thirty-five to fifty degrees, being throughout quite smooth and covered with a heavy coating of clay.

The fragments of rock that fell into the chasm during the time it was being charged with the precious metals, formed each a nucleus about which the quartz and ores collected. In all parts of the vein are to be seen pieces of country rock, from the size of a filbert to many pounds in weight, about which quartz has formed, and with the quartz ore.

After the vein was filled, it appears to have again several times opened, when fresh fragments fell into the newly formed fissures, and were surrounded by quartz and ores by the action of the waters and gases forced up from below. These several convulsions pulverized the quartz and ore previously formed in the vein, leaving it in such a condition that in most of the mines the greater part of it can be dug down with picks.

In most places in the ore-bodies in the lower levels, appearances indicate that while the ore and quartz were in this shattered and pulverized state, floods of hot water poured in upon it and boiled it as in a caldron, and that at the end of this cooking operation it finally settled down, assuming a horizontally stratified position. In this way must have been formed the occasional streaks of clay and the numerous strata of various shades of color and degrees of fineness of subdivision of component parts seen in the ore as it now rests in the vein. It is as plainly sedimentary in form as any gravel deposit seen on the surface. This is not seen everywhere in the lower levels, but in such places as were most subject to dynamical action.

All who have visited the lower levels of the mines on the Comstock lode must have observed, even upon the most cursory examination of the ores, the peculiar stratification[stratification] of which I speak. The chasm in which is formed the Comstock lode was doubtless at one time a seething caldron, and at the great depths now attained, not only great quantities of hot water are found, but the rock itself is in many places sufficiently hot to be almost painful to the naked hand.

The course or “strike” of the Comstock vein is a little east of the magnetic meridian, about north twenty-five degrees east. The lode crops out in several places along the face of Mount Davidson, throwing up huge piles of quartz at intervals of from three hundred to five hundred or one thousand yards, as it takes its course southward across the “Divide,” and through and beyond Gold Hill; also, to the northward, in the direction of Cedar Hill and Seven-mile Cañon. When the ledge crops out it has a first or false dip to the west, but after being followed down it becomes straight, then turns, and takes its regular dip to the east at an angle of from thirty-five to fifty degrees. In the Ophir, when the true dip was first discovered, the vein turned to the east at the depth of three hundred and thirty feet. The croppings of the vein being above and to the west of Virginia City, this eastern dip carries it under the whole length and breadth of the town, and it also passes under the town of Gold Hill, a mile further south in the same way.

The lead follows the curved outlines of the hills on the surface, swinging in at the ravines and bearing out on the points of the ridges, but as depth is attained it will doubtless be found to straighten in the direction of its present general course. The only gangue of the vein is quartz, though, in places, there are found detached patches and masses of gypsum and carbonate of lime. The ore contains native gold, native silver, sulphuret of silver (silver glance), stephanite, chloride of silver, some rich galena and antimony, and a few rare forms of silver in small quantities; also, mingled with the whole mass of the ores, iron pyrites, copper pyrites, zinc-blende, and a few other minerals.

The early miners began the work of opening their claims along the Comstock by sinking shafts on the croppings and by running short tunnels to pass under these croppings and tap the vein at depths varying from two hundred to six or seven hundred feet. The shafts were mere circular holes precisely like an ordinary well, and a common windlass, rope, and bucket, constituted all there was coming under the head of machinery.