Page:The American Cyclopædia (1879) Volume X.djvu/261

 LEAD 255 ments of sandstone, magnificent bunches of quartz crystals, and lumps of lead and copper ores; and its walls were also lined in places with the same Ores. In these features a stri- king resemblance is exhibited to the " open- ings " in the western lead mines, although found there only in limestone. The vein is moreover like those of the western mines in lacking veinstones, and probably also in being limited to certain rock formations, be- neath which it will not prove productive. In Chester and Montgomery cos., Pa., near Phcenixville, is a group of lead and copper mines, in a small district of only 5 or 6 m. in length by 2 or 3 in breadth, some of the re- markable productions of which have already been noticed. They occur in gneiss and the red shale and sandstone of the middle secondary, cutting the strata in direction and dip. Nearly all the veins, of which there are 12 or more, are parallel to each other, directed N. 32-35 E. and dipping steeply S. E. When confined chiefly to the gneiss, they produce as a general rule lead ores; when included in the red shale, their principal product is copper ores. Quartz and iron pyrites make up the larger part of the lodes, the latter in the upper portions of the mine decomposed to a soft brown gossan. This material sometimes yields 10 oz. of silver to the ton. Prof. H. D. Rogers, from whose " Geology of Pennsylvania " these data are obtained, enumerates the following large vari- ety of metallic constituents of the Wheatley lode, besides the gangue of quartz and sulphate of baryta : of lead sulphate, carbonate, phos- phate, arseniate, molybdate, chrpmate, tung- state, chromo-molybdate, arsenio-phosphate, sulphuret, and antimonial argentiferous; of zinc sulphuret, carbonate, and silicate; of copper native metal, sulphuret, black oxide, malachites green and blue ; of iron the oxide containing silver, pyrites, brown spar, and hematite; native silver; black oxide of man- ganese, and native sulphur. Gersdorfite, or sulph-arsenide of nickel, has also been found. This mine was opened in 1851, and up to September, 1854, had produced, according to the manager's report, 1,800 tons of lead ore, principally phosphate, estimated to yield 60 per cent, lead. The Chester county mining company commenced operations in 1850 in the same vicinity, and up to November, 1851, had smelted 190,400 Ibs. of dressed ore, almost exclusively phosphate, which produced about 47 per cent. lead. Dr. Genth found this kind of ore to contain 1-6 oz. of silver in 2,000 Ibs. ; the coarsely granular galena gave 16*2 oz., and the -radiated and finely granular galena 11 '9 oz. Operations ceased at these and the other adjacent mines in 1854 and 1855. In S. W. Virginia and E. Tennessee many lead mines, not in the metamorphic belt, but in the great Silurian limestone formation of the valley of Virginia, have been worked with greater or less success for many years past, their ores being compact and crystallized carbonate of 484 VOL. x. 17 lead as well as galena. Those belonging to the Wythe union lead company on New river, Wythe co., Va., are known to have been pro- ductive in 1754, and are still worked. All the mines of this region resemble in their geologi- cal associations and metallic products those of the western lead region. The Washington mine, Davidson co., N. C., has attracted in- terest on account of its being the only mine in the United States that has produced much silver. It was opened in 1836 in the silicious and talcose slates of the gold region, and, like most other veins of the metamorphic rocks of this region, has the strike and dip of the strata. There are two parallel veins worked together, which dip steeply toward the north. They are underlaid by a granitic rock, and above is talcose slate. The mine was commenced for the carbonates of lead, which were found in considerable quantity in a heavy dull ore of earthy appearance, and also in glassy crystals. Some galena and phosphate were also met with. It was not until after smelting large quantities of these ores that native silver was discovered, and the argentiferous character of the lead ores. In 1840 the display of native silver in arborescent forms and disseminated through the magnesian veinstones was very striking, and excited expectations of great richness at lower depths; but the rich and easily reducible carbonate of lead was soon ex- hausted, the ore in greater depths consisting of zinc blende and argentiferous galena which presented difficulties in treatment. Till 1844 the mine continued to produce largely rich argentiferous ores, after which the ores gradu- ally diminished in quantity ; the yield of that year is stated to have been $24,009 of silver and $7,253 of gold, separated from 160,000 Ibs. of lead, an average of 240 oz. of auriferous sil- ver to 2,000 Ibs. In 1851 the production was 56,896 Ibs. of lead and 7,942-16 oz. auriferous silver, equal to 279 oz. to the ton of lead. Dr. Genth found the proportion of silver in the sulphurets very variable, running from 2'5 to 19-5 oz. to 2,000 Ibs. An average sample taken from 2,000 to 3,000 tons of ore (1849) con- tained 45 per cent, of zinc, 21 per cent, of lead, and about 8 oz. of silver to the ton, with minute quantities of copper and gold. In 1852 mining operations were stopped as unprofitable, but were soon after renewed, and have since been continued intermittently. The mine was ac- tively worked during the civil war by the con- federates for lead. In 1871 it was 650 ft. deep, and produced about 400 to 500 tons of ore per month, part of which was slaty and required dressing. There are numerous well developed lead veins in the azoic of northern New York. The most important are those of Rossie in St. Lawrence co., which are particularly famous for the magnificent crystallizations of calcite and galena. Although occurring in the older rocks, the galena is almost entirely free from silver. The Coal Hill vein, 2 ft. wide, in gneiss, was worked with great activity in 1837 and