Excerpt from The Nature of Ore Deposits, Vol. 1 of 2 In a mineralogical sense an ore is a metalliferous mineral or a mixture of such minerals. Practically, however, this definition of an ore must be qualified by the statement that only those minerals and mixtures of minerals are ores from which metals or metallic compounds may be produced on a commercial scale and at a profit. Two examples of equal mineralogic or petrographic value may differ materially: a basalt carrying enough, magnetite to influence the magnetic needle, but yet containing less than 10 per cent of iron, is far from being an iron ore. On the contrary, a vein with a silver content of only 0.5 per cent is an ore deposit, since with this content it is commercially valuable. In the ease of a gold deposit the amount sufficient to distinguish a gold ore from barren rock may be even less, for in California and Dakota gold ores with only from 4 to 6 grains per ton of gold are exploited. Hence it is the economic point of view that must always be borne in mind, the profit of working being subject to variation in the course of time.

While nickel and cobalt were formerly nicknames for materials which were thrown upon mine dumps as useless, and were considered as a mere nuisance in silver mining, today the compounds of these metals and the associated minerals are in great demand as ores. To a certain degree a mineralized material may be an ore in one locality and yet not be an ore in another place, the cost of reduction depending on the proximity to lines of traffic and cheap freights. The science of ore deposits is, in other words, the study and consideration of the deposition, distribution and origin of rock bodies containing ores in such quantities that they may be extracted profitably by mining operations. The science of ore deposits is a branch of geology which can only be understood and practiced by those who have some knowledge of that science, particularly of petrography, and of course, also, a knowledge of mineralogy and chemistry. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This 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.