Economic Geology Of The Mercur Mining District Utah PDF Download

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1895. Not illustrated. Excerpt: ... regard to the detailed structure of the gold deposit have been obtained, the owners and superintendent having lent their aid in every way to its full investigation. The Mercur ore bodies will therefore be described in considerable detail. MERCUR MINE.' UNCLE SAM TUNNEL. This is the most southerly in the series of tunnels in the Mercur mine which have been or are actually productive of ore. The mine is Flo. 42--Banding in altered porphyry. opened by means of these tunnels, which are driven into the side of the hill at the outcrop of the altered zone along the strike of the beds. The mouths of the tunnels, viewed from a distance, afford a very good indication of the position of the ore sheet. At the entrance to the Uncle Sain tunnel the open cut shows at the top a thickness of 4 or 5 feet of soft, shaly stuff, of various alternating shades of brown, gray, and yellow. This is undoubtedly altered Eagle Hill porphyry. It is the characteristic roof of the ore sheet, and among the miners goes by the name of "shale." Immediately below this altered porphyry zone comes decomposed limestone, containing about one-third in bulk of soft, pulverulent stuff', which incloses bowlders of hard, blue lime and of chert, making up the other two-thirds of the rock. The bowlders have been formed in place by decomposition extending from the fissures and joint and bedding planes inward; and the gray pulverulent matter which surrounds them is the product of their alteration. It is very much like the product of the alteration which takes place under atmospheric influences, such as has already been noted in the general description of the limestones of the district. There is only about 5 feet in which the proportion of the altered to the unattacked limestone is as above indicated, for the al...