210 Proceedings 



Program : 



Some Reported Gold Discoveries in the Northwestern 

 States, by C. W. Hall. 



Dr. U. S. Grant gave an account of the Rainy Lake gold 



region. 



[abstract.] 



Rainy Lake lies in an area of crystalline and highly folded rocks, 

 which have been separated by Lawson into two series called Coutchich- 

 ing and Keewatin. The former series consists mainly of mica-schists, 

 while the latter consists of various slates and schists, among which 

 greenstone schists and also massive greenstones are common. Travers- 

 ing these rocks are quartz veins, some of which carry values in gold. 

 The best veins lie either in the green schists or in other rocks of igne- 

 ous origin, and the most promising prospects occur on the Canadian 

 shores of the lake. (An account of this district has been published in 

 the 23d Annual Report of the Geological and Natural History Survey 

 of Minnesota, pp. 36-105, 1895, under the title "Preliminary Report on 

 the Rainy Lake Gold Region," by H. V. Winchell and U. S Grant; also 

 in Vol. 4 of the Final Report of the sr.me survey, pp. 192-211, 1899.) 



C. P. Berkey read a paper on An Improved Method for 

 Quantitative Determination of Antimony, Zinc, Iron, Copper, 

 and Lead in an impure Galena ore. 



[abstract.] 



The investigation and experiences resulting in these notes arose 

 over a particular ore brought from the Kootenai country in British 

 Columbia. Mr. Stevenson, a special student in the laboratories of the 

 University of Minnesota, was equally interested in them. 



The ore contains from 50% to 80% metallic lead which is in the 

 form of the natural sulphate, PbS. The impurities which make up the 

 rest of the required amount are antimony, zinc, iron, copper and sili- 

 ceous gangue matter. Antimony is the most common impurity and 

 occurs in largest amount next to lead. It is in the form of sulphide 

 Sb, S3. It was chiefly in the effort to determine this constituent that 

 the first and greatest difficulty arose. The natural association seemed 

 to have so thoroughly satisfied the chemical affinities that the usual 

 methods of solution were ineffectual, and separation did not occur 

 where it was calculated to. Iron and zinc occur in similar amount, 

 both in sulphate form, FeS.. and ZnS. Copper is not always present 

 in quantity of importance, but occasionally in considerable amount 

 with iron as chalcopyrite, CuFeSo. The siliceous gangue is present 

 in amount varying from to 15% according to quality of the ore. 



The first difficulty was in securing complete solubility of the ore, 

 the next was the almost constant failure to obtaiu precipitates of any 



