Mohave County miner., 1913-09-06
Low Ores are Enriched
 for the Use of Man.

rocks, many of the familiar metals, es- !! pecially copper, lead, zinc, silver and quicksilver, exist as phides-that is, as minerals composed of one or more metals chemically combined with sulphur. In such original or primary deposits the generally worth less iron sulphide, pyrite, is likely to predominate, while the more valuable metals may be present in quantities too small to be profitably extracted.
 In the coarse of geological ages, however, as the land wears down under the ceaseless attack of weather and running water, the primary ore deposit, with it's small proportion of valuable metals, is itself exposed to the forces of disintegration and decay that are operating over all land sur faces on the globe. Some constituents of the disintegrating ore are carried away by winds, and others, particular ly some of the metals, are dissolved and carried by percolating rain water down into the earth. These metal charged solutions, coming into contact with the sulphide minerals of the rocks, have the chemical property of transforming these sulphides into others more valuable to man. Thus solutions carrying copper and coming into contact with pyrite, which is a mineral compound of sulphur and iron, abstract some of the iron and leave the copper in its place. The bright yellow, beautiful but generally useless pyrite may be changed, for example, to the less brilliant dark.gray but far more valuable mineral chalcocite, a sulphide of copper. This natural chemical concentration, whereby, as the exposed upper portion of an ore body decays and is removed by erosion, it's valuable constituents are in large part carried down and added to the portion that remains, is an exception ally important process and one that has played an essential part in the formation of many large and produc' tive bodies of ore.
 Growing recognition of the over. whelmlng importance of enrichment in the formation of some of the largest copper deposits of the world dates from the year 1900 and is due chiefly to the work of American geologists recent publication of the United States Geological survey Bulletin 529 entitled "rhe Enrichment of Sulphide Ores," by w. H. Emmons, is devoted to the description and discussion O tended to bring together all the in formation at present available or downward sulphide enrichment, is di visable into two parts. The first par deals with the various conditions, sucl as climate and porosity of the rocks that influence the process and with th physical and chemical principles in volved,
 The second part reviews briefly th available knowledge of North Ameri can mining districts in so far as thi knowledge bears on the problem o enrichment. The chemistry of enrich ment is very fully discussed in connec ton with the various minerals foun in ore deposits, and the students of or deposition will find the book invalu able as summary of what is know on the particular subject treated as
 guide to the literature that relates t it.
 The prese nt publication, like Clarke Data of Geochemistry, Bulletin 49 of the United States Geological SUI vey, illustrates the effort now ben made by the survey to bring together for convenient reference by busy mer data now scattered not only throug it's own reports but in other public; tons also, Such volumes, however are not mere compilations. The pr, viously published material is enriche by new observations and is illuminate by discussion in the light of the late, scientific knowledge.
 "The Enrichment Of ulphide Ores, Bulletin 529, may be obtained free c application to the director. Unite States Geological survey, Washington D. c. The demand for the second ed tion of "The Data of Geochemistry