(h.) The group of mines opened on the American Fork, on Big and Little Cottonwood, and in Parley's Park, including the Silver Bell, the Emma, the Vallejo, the Prince of Wales, the Kessler, the Bonanza, the Climax, the Piñon, and the Ontario. (The latter, the greatest silver mine now known in the country, lies in quartzite, and the trap is near, but not in contact with the vein.)
(i.) In Nevada, the ore deposits of Pioche, Tempiute, Tybo, Eureka, White Pine, and Cherry Creek, on the east side of the State, with those of Austin, Belmont, and a series too great for enumeration in the central and western portions.
(j.) In California, the Bodie, Mariposa, Grass Valley, and other mines.[1]
(k.) In Idaho, those of the Poor Man in the Owyhee district, the principal veins of the Wood River region, the Ramshorn at Challis, the Custer and Charles Dickens, at Bonanza City, etc.
[Footnote 1: See Redmond's Report (California Geol. Survey Mining Statistics, No 1), where seventy-seven mines are enumerated, of which three are said to be in "porphyritic schist," all the others in granite, mica schist, clay, slate, etc.]
In nearly all these localities we may find evidence not only that the ore deposits have not been derived from the leaching of igneous rocks, but also that they have not come from those of any kind which form the walls of the veins.
The gold-bearing quartz veins of Deadwood are so closely associated with dikes of porphyry, that they may have been considered as illustrations of the potency of trap dikes in producing concentration of metals. But we have conclusive evidence that the gold was there in Archæan times, while the igneous rocks are all of modern, probably of Tertiary, date. This proof is furnished by the "Cement mines" of the Potsdam sandstone. This is the beach of the Lower Silurian sea when it washed the shores of an Archæan island, now the Black Hills. The waves that produced this beach beat against cliffs of granite and slate containing quartz veins carrying gold. Fragments of this auriferous quartz, and the gold beaten out of them and concentrated by the waves, were in places buried in the sand beach in such quantity as to form deposits from which a large amount of gold is now being taken. Without this demonstration of the origin and antiquity of the gold, it might very well have been supposed to be derived from the eruptive rock.
Strong arguments against the theory that the leaching of superficial igneous rocks has supplied the materials filling mineral veins, are furnished by the facts observed in the districts where igneous rocks are most prevalent, viz.: (1.) Such districts are proverbially barren of useful minerals. (2.) Where these occur, the same sheet of rock may contain several systems of veins with different ores and gangues.
The great lava plain of Snake River, the Pedrigal country of eastern Oregon, Northern California and Mexico are without valuable ore deposits. The same may be said of the Pancake Range and other mountain chains of igneous rock in Nevada, while the adjacent ranges composed of sedimentary rocks are rich in ore deposits of various kinds. A still stronger case is furnished by the Cascade Mountains, which, north of the California line, are composed almost exclusively of erupted material, and yet in all this belt, so far as now known, not a single valuable mine has been opened. In contrast with this is the condition of things in California, where the Sierra Nevada is composed of metamorphic rocks which have been shown to be the repositories of vast quantities of gold, silver, and copper. Cases belonging to this category may be found at Rosita and Silver Cliff, where the diversity in the ores of the mines already enumerated can hardly be reconciled with the theory of a common origin. At Lake City the prevailing porphyry holds the veins of the Ute and Ulay and the Ocean Wave mines, which are similar, and the Hotchkiss, the Belle, etc., entirely different.
We have no evidence that any volcanic eruption has drawn its material from zones or magmas especially rich in metals or their ores, and on the contrary, volcanic districts, like those mentioned, and regions, such as the Sandwich Islands, where the greatest, eruptions have taken place, are poorest in metalliferous deposits.