Excerpt from The Enrichment of Ore Deposits The problems of superficial alteration and enrichment are not simple. Not only do the several metals segregate in different ways, but each metal may behave differently in different mineral associa tions. Every district and every deposit should be studied separately in the light of all available chemical and geologic data. There are, however, certain laws Of segregation that almost invariably are clearly indicated, and as data have accumulated many puzzling ap parent exceptions to these laws have disappeared. This paper is an amplification of, an earlier Survey bulletin on the enrichment of sulphide ores (bulletin It is a discussion of representative deposits, especially Of the paragenesis of their ores and of the principles that underlie the processes of enrichment. I hope it may suggest to those engaged in geologic work and in mining some lines Of approach to the solution of the complex problems that are encountered in the field. I realize fully that there may be serious omissions and possibly errors in the discussion of the complex problems here presented. I shall esteem it a favor if anyone whose statements I may have mis quoted or misinterpreted will set me right, and if those who have had superior opportunities for study Of certain districts will correct any wrong impressions that I may have given. 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.

Of results -- Introduction -- Physiography -- Geology -- Metasomatic alteration of the rocks by hot solutions -- Summary of geologic history -- Mineralogy of the San Francisco region -- Ore deposits -- Genesis of the ores -- Origin of ore-bearing solutions -- Alteration of ores -- Suggestions as to prospecting -- Future of the region -- Detailed descriptions of mines -- Index.

The problem of time-and strata-bound formation of ore deposits has during the past decade become one of the most debated topics in cur rent international discussion. Due to the amazing results of modern mineral exploration and world-wide geophysical research, the mutual relationship between the complex geological history pf a crustal seg ment and the development of distinct metallogenic provinces (ore belts) has received much interest. Reviewing the earth's history in this light one can now recognize metallogenic epochs even of global range which document the existence of world-wide time-bound ore enrich ments. The knowledge of these metallogenetic processes has been growing step by step for several decades. It began with simple observations and sceptic interpretations, which at first threw heretical spot lights on to the edifices of the prevailing theories on granitic differentiation as the favoured source of ore deposits. It was obvious that the new ideas at first referred to ore enrichments in sedimentary sequences, nowadays summarized under the term strata-bound, and mainly interpreted as stratiform or sedimentary ore deposits. Moreover, the modern term "strata-bound" also includes ore mineralizations which are bound to distinct units of layered (intrusive or extrusive) igneous complexes as a general descriptive term without genetical restriction! Albert Maucher is one of the representatives of the initial era who discussed these genetical questions critically in the decade before the 2nd World War.