University of Nevada, Las Vegas

Goldfield Mascot Mining Company p 11

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PARALLEL ZONES So far, however, as development has proceeded, the district appears to comprise a parallel series of mineral-bearing zones or belts, some five or six in number, from 1,000 feet to 3,000 feet in width.The veins run in various directions, but chiefly parallel to that of the zone in which they are found. There are also, however, numerous cross-veins, some running, north and south, others east and west, and as usual in mining regions, the greatest deposits of ores are found at and surrounding these places of vein intersection.The deepest developments thus far are in the Jumbo mine, 500 feet deep, but little is generally known regarding the character and amount of ore exposed in the veins at that depth.Diamond drills have shown the existence of ore bodies which do not appear at the surface, and it is very certain that many more will be found which have no actual outcrop.SECONDARY ENRICHMENTThe veins are in the nature of fissures in which there has been large replacement of the adjoining country rock by quartz as well as the quartz deposit within the walls of the crevices themselves. In the oxidized portions of the vein the gold is largely free and frequently very clearly visible. In the sulphide zone, which is reached about 130 feet below the surface, copper sulphides appear (bornite and tetrahedrite), also bismuth sulphides and some little tellurides, There is a zone of secondary enrichment in the upper portion of the sulphides or live ore, the thickness of which has not yet been determined, but which contains extremely rich free gold deposits, due to the values added by reason of re-deposition of gold leach from the more superficial ores. These values are so extraordinary as to surpass any district thus far discovered in the United12

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