PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 298th meeting was held in the lecture room of the Cosmos Club 

 on October 27, 1915. 



INFORMAL COMMUNICATIONS 



G. F. Loughlin described an occurrence of hubnerite, wolframite, 

 pyrite, etc., at Leadville, in deposits intermediate in nature between 

 contact metamorphic deposits and ordinary veins. 



W. F. Hillebrand exhibited a liquid alloy composed mostly of gal- 

 lium, with a small percentage of indium and zinc. This had been pro- 

 duced in a zinc metallurgical plant, appearing as drops sweated out of 

 zinc-lead dross-plates. It was learned by correspondence with the 

 manager of the works that the particular ore from which it had been 

 derived was uncertain and that in any case the amount which could be 

 produced was probably small. 



In reply to questions from Spencer, Martin, and Wells, Hille- 

 brand said that at present there was no use to which gallium was put. 

 It has been obtained previously from zinc ores and indications of its 

 presence were often found in spectroscopic work. 



REGULAR PROGRAM 



E. T. Allen: Chemical studies in copper sulphide enrichment. It 

 was shown from a study of the copper sulphides that chalcocite was a 

 mineral of variable composition, made up of cuprous sulphide with a 

 varying amount of dissolved cupric sulphide. There are two crystal- 

 line forms of cuprous sulphide, with a transition point at ,91°. Only 

 the lower temperature form has so far been found in nature. It was 

 explained how the system Cu-Fe-S was being studied through the 

 dissociation pressure curves of the various sulphides of Cu and Fe. 

 A preliminary study of gossans has been made, with the result that all 

 appear to be amorphous and to show a thermal behavior similar to 

 limonite. A comparative study of the rates of oxidation of the com- 

 moner sulphides, in pure condition, has been made and much atten- 

 tion has been given to the chemical study of the enrichment process. 

 The action of copper sulphate solutions on the most important sul- 

 phides has been studied at 200°, 100°, and 40°. In all cases the final 

 product has been cuprous sulphide. Covellite, and chalcocite con- 



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