In these widely separated localities are to be found fissure, segregated, and gash veins, and a great diversity of ores, which have been derived, sometimes from the adjacent rocks--as in the segregated veins of the Alleghany belt and the gash veins of the Mississippi region--and in other cases--where they are contained in true fissure veins--from a foreign source, but all deposited without the aid of superficial igneous rocks, either as contributors of matter or force.
2. In the great mineral belt of the Far West, where volcanic emanations are so abundant, and where they have certainly played an important part in the formation of ore deposits, the great majority of veins are not in immediate contact with trap rocks, and they could not, therefore, have furnished the ores.
A volume might be formed by a list of the cases of this kind, but I can here allude to a few only, most of which I have myself examined, viz.:
(a.) The great ore chambers of the San Carlos Mountains in Chihuahua, the largest deposits of ore of which I have any knowledge. These are contained in heavy beds of limestone, which are cut in various places by trap dikes, which, as elsewhere, have undoubtedly furnished the stimulus to chemical action that has resulted in the formation of the ore bodies, but are too remote to have supplied the material.
(b.) The silver mines of Santa Eulalia, in Chihuahua, from which during the last century one hundred and twelve millions of dollars were taken, opened on ore deposits situated in Cretaceous limestones like those of San Carlos, and apparently similar ore-filled chambers; an igneous rock caps the hills in the vicinity, but is nowhere in contact or even proximity to the ore bodies. (See Kimball, Amer. Jour. Sci,. March, 1870.)
(c.) The great chambers of Tombstone, and the copper veins of the Globe District, the Copper Queen, etc., in Arizona.
(d.) The large bodies of silver-ore at Lake Valley, New Mexico; chambers in limestone, like c.
(e.) The Black Hawk group of gold mines, the Montezuma, Georgetown, and other silver mines in the granite belt of Colorado.
(f.) The great group of veins and chambers in the Bradshaw, Lincoln, Star, and Granite districts of Southern Utah, where we find a host of veins of different character in limestone or granite, with no trap to which the ores can be credited.
(g.) The Crismon Mammoth vein of Tintic.