The Formation Of Gold Nuggets And Placer Deposits

THE origin of gold both in placer deposits and in veins, and especially the origin of nuggets, has been the subject of repeated discussions and investigations, which have been recently brought to my attention by several extremely interesting specimens sent to me for examination, and more especially by the one exhibited at the meeting of the Institute in February, 1880.* In the year 1874 I made some examinations of the hydraulic mines of Califor¬nia, and was very much struck with the distribution of the gold throughout these deep placers, which were almost invariably poor on' the surface, while gradually growing richer towards" the bed¬rock. The constant presence of fossil wood, and the large quantity of organic matter contained even low down in these beds, was also remarkable. Not being satisfied with the various theories advanced to account for the formation of these deposits, I began an investiga¬tion early in the year 1879 on the conditions of solubility of gold and the causes of the loss in working gold ore in a large way: The researches which I have undertaken show that gold must be considered a soluble rather than an insoluble metal, and that the conditions of solution are such as will be found anywhere where gold is likely to occur, and the solution may take place even under the ordinary cir¬cumstances of surface drainage, and may be going on freely even where the presence of gold has never been suspected, and that there are causes enough in nature to produce the solution of the gold in sufficient quantities to account for all the phenomena of both the vein and placer formations. The general theory with regard to the formation of these placer deposits and nuggets has been that they were the result of the de¬struction of pre-existing- vein-matter, which does not accord with the facts as shown in the deep placer deposits. The gold in such case would be distributed in layers of unequal richness throughout * Transactions of the American Institute of Mining Engineers, vol. 8, p. 451.