Show HOW BONANZA ORE BODIES ARE FORMED the enrichment of ore deposits is a most interesting scientific problem and during the last fifteen years the methods of such enrichment have become fairly well understood the study of these methods has proved to be of considerable economic value for its results have been successfully used in the exploitation of many mineral deposits the united states geological survey has been active in the study of the principles and methods of the enrichment of ore deposits and has recently published a report on the subject by W H emmons united states geological survey bulletin the theory of ore enrichment may be briefly stated as follows mineral deposits that are exposed to weathering that is to the action of the atmosphere of rain frost and other agencies break down and form soluble salts and new minerals that remain unchanged under surface conditions in the course of weathering however the ore of each metal behaves in its peculiar way deposits of iron aluminum manganese and some deposits of gold and other metals may be enriched near the surface by the removal of 0 valueless material on the other hand many of the valuable metals including clouding in copper silver and less commonly gold zinc and lead go into solution and are carried downward by rain water and and thus parts of the ore bodies may be enriched most of the rich or bonanza ore bodies of copper many of silver and some of gold and other metals have been formed in in this way bulletin describes in detail the geologic conditions favorable and unfavorable to the formation of enriched mineral deposits and gives a summary of the criteria by which such deposits may be recognized the natural chemical processes by which enrichment is produced are fully described and the behavior of each metal is considered separately and is illustrated by descriptions of practically all its known valuable enriched ore bodies although the paper is of necessity rather technical it is by no means abstruse and the matter it contains should be of great value not only to the scientific student but to the mine operator who is concerned only with the profitable exploitation of ore deposits |