. Mining and Scientific Press . ney-like veins in the limestone as a-e, i b, and </-/ which strike north and south and ascend from such con-tact nodes as <, h, and / to the surface: and (3) i-ross-fissures which occasionally conned the veins of class (2).The ; for smelting is that of < lass i 1 i which, when in place, contains from 6 to 10, of lead. The old stope-tillings. as now shipped for smelting, contain 2 to 3%lead, under 50?! of silica, 8 grammes of gold, and 200 to250 gm. of silver per ton. The veins of Class (2) con-tain 60 to 80ri of silica; when large, they are the richesti
. Mining and Scientific Press . ney-like veins in the limestone as a-e, i b, and </-/ which strike north and south and ascend from such con-tact nodes as <, h, and / to the surface: and (3) i-ross-fissures which occasionally conned the veins of class (2).The ; for smelting is that of < lass i 1 i which, when in place, contains from 6 to 10, of lead. The old stope-tillings. as now shipped for smelting, contain 2 to 3%lead, under 50?! of silica, 8 grammes of gold, and 200 to250 gm. of silver per ton. The veins of Class (2) con-tain 60 to 80ri of silica; when large, they are the richestill gold; when small, they consist mainly of iron oxides,poor in precious metal, like the fissures of Class (3).The dividing line for the content of FeO is about 50%;above that amount the orebodies are apt to be commer-cially worthless as far as gold and silver are main working adit for present operations at theVictoria group runs north and south in the porphyryfrom e (Fig. 1). It is provided with double tracks for. 1lG. 1. GEOLOGIC SECTION OF SAN PEDRO handling Koppel H-ton steel ore-cars which descend bygravity when loaded and outward bound. When emptythey are hauled back by mules to the interior of the the cars are also of Koppel make but have tobe contracted in size in order to enter the shaft cages, andonly hold 600 kg. The adit cars discharge into side-dumpwooden cars—holding 4 to 5 tons—that are handled onthe surface tramway, in trains of 10, by a Porter com-pressed air locomotive. This tramway connects all theprincipal mines of San Pedro, and forms a feeder for therailway from Rio Verde to the smelter at Morales. Belowtlie adit -, the lower levels are developed by inside verticalwinzes. The cross-cut eh connects the adit with the? Eidalgo winze / //, from the bottom of which the cross-cut // q1 the lime-porphyry contact again at b. Froml[ I, the Begonia winze b-B has been sunk, from thelow< st point of which another cross-cut B-f cuts
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