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Show 582 WESTERN WILDS. " That is never found with silver." The enclosing rocks, known in reference to the vein as " wall rock," and when spoken of generally as the " country rock," are somewhat more simple in construction. Of the elements in rock and mineral, the first is Oxygen. This constitutes nearly one- half of the earth's crust; it enters into all rocks and nearly all minerals. Next to it is Silicon. This makes up about one- fourth of the earth's crust. So oxygen and silicon alone constitute about three- fourths of all the mate-rials the miner has to deal with. Combined in some way they make . Quartz. This is, in general terms, the matrix of the precious metals that is, the atom of silver or gold is inclosed by atoms of quartz, so that the metal, as such, is rarely visible, and its presence is known to the experienced miner only by various signs. But if there is much galena present with the silver, that metal nearly always shows brightly with its cubical crystals, looking like marvelously rich ore. If, on the other hand, the silver is a chloride or sulphuret, there is no luster. Thus the richest ore always looks worthless to the pilgrim, and the cheapest looks the richest the quartz in either case merely aiding to obscure the true ore. Next in rank, probably, is Feldspar. A general name given to a class containing several varieties. Next is Mica. Which is too well known to need description. Quartz, feldspar, and mica, combine to make granite, in which the shining specks, or flakes, of mica may often be distinguished. Th6 last I need mention is Lime. A word used by the miner in a very general sense indeed, and without reference to the many distinctions made by science. The practical miner lumps it all together under the general name of lime-stone. Limestone is the country rock of all the Cottonwood, Ameri-can Fork, and Ophir Districts in Utah ; of the immediate vicinity of Leadville ; of some of the richest mines in Mexico, and of many other districts. In eastern Colorado we usually find granite, or some massive rock; and in other districts the varieties are many. With these definitions you may form some idea of what the miner means by his first question about a new district: " What is the country rock?" That answered, he at once has some idea as to the value of the mines, for in some mysterious way the inclosing rock has deter-mined the ease with which the ore can be worked, and to some ex- * I tent its richness. For instance, carbonic acid being present in lime-stone, the reader will easily see why mines yielding carbonate ores must have one wall of that rock. The carbonic acid has been ab- |
