. Transactions. Fig. 21.—View Showing Limestone Weathering in One of the Mine-Openings at Austinville, Wythe County, Fig. 22.—View Showing Limestone Weathering in One of the Mine-Openings at Bertha, Wythe County, Va. 714 LEAD- AND ZINC-DEPOSITS VIRGINIA-TENNESSEE REGION. of the decay, shown in specimen III., the results are markedlydifferent; the more refractory constituents, which are presentin the fresh rock in barely more than traces, are retained asthe principal ingredients composing the residual clay. Thecarbonates of lime and magnesia, which practically make upthe fresh rock, have s
. Transactions. Fig. 21.—View Showing Limestone Weathering in One of the Mine-Openings at Austinville, Wythe County, Fig. 22.—View Showing Limestone Weathering in One of the Mine-Openings at Bertha, Wythe County, Va. 714 LEAD- AND ZINC-DEPOSITS VIRGINIA-TENNESSEE REGION. of the decay, shown in specimen III., the results are markedlydifferent; the more refractory constituents, which are presentin the fresh rock in barely more than traces, are retained asthe principal ingredients composing the residual clay. Thecarbonates of lime and magnesia, which practically make upthe fresh rock, have suffered most from solution and removal,and are only present in the residual clay in very small amounts. XIII. Age. Since the ores have been shown to follow rather closely thefaulted breccia-zones, they were formed after the period ofdeformation which resulted in the folding, faulting and shat-tering of the limestone near and along the lines of period of deformation probably dates back to late in, orafter the close of, the Carboniferous. The original sulphideores must antedate the secondary ores, sinc
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
