Excerpt from Lead OresLead, although one of the commoner of the base metals, is present in the earth's crust only to the extent of a fraction of I per cent. Of the whole. In workable deposits, however, the proportion is much higher owing to a natural concentration of material. Lead is closely associated in nature with zinc, and their primary or sulphide ores commonly occur together. Zinc ores are more soluble than lead ores, hence in the zone of oxidation the former have frequently been leached away, and practically pure lead ore may occur above water - level. In this way were formed the lead carbonate deposits of Lead ville and elsewhere. Such bodies, however, give place to mixed lead and zinc sulphides in depth. Lead in nature is also intimately associated with silver, and many lead deposits are also the repositories of valuable silver ores. Galena itself is frequently argentiferous and may be regarded as the chief source of the world's supply of silver.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.