140 Wisconsin Academy of Sciences^ Arts^ and Letters. 



ON THE OCCURRENCE OF GOLD AND SILVER IN 

 MINUTE QUANTITIES IN QUARTZ FROM CLARK 

 COUNTY. 



BY K. D. IRVING, A. M., M. E. 

 ProfesBor of Geology in the University of WisconBin. 



In the fall of 1871, some samples of quartz from Clark 

 county, Wis., were handed me by Mr, Geo, W, Brown, with a 

 request for an assay for Gold and Silver, The samples were 

 barren looking, tough, white quartz, presenting none of the 

 reddish or rotten appearance common to surface Gold ores of 

 any value. Scattered throughout the quartz, were small 

 quantities of Magnetite in scales, Pyrite and Arsenopyrite ; 

 this association being a usual one in Gold quartz. Mr. Brown 

 pointed out the locality from which the samples came in Clark 

 County just north of the junction of the Potsdam Sandstone 

 with the Eozoic rocks. He represented the prevailing rocks 

 in that section as Chloritic and Talcose Schists ; and of the 

 former he brought me fine specimens. The quartz he repre- 

 sented as occurring in veins ; though his samples seemed to 

 have been selected from loose masses. I need hardly say that 

 these associations are the common ones in Gold regions. On 

 taking the usual amount, four (1) Assay Tuns., or about 120 

 grns., the resulting button of bullion weighed just enough in 

 excess of the Silver in the Litharge used, to make me suspect 

 the presence of Gold in the quartz. On dissolving the button 

 in Nitric Acid, one or two small flakes remained, but not 

 enough to weigh. I then took for a second Assay, four times 

 the usual quantity and obtained a weighable amount of gold, 

 corresponding to about 20 cts per 2,000 lbs of ore. 



Mr. Brown subsequently, at my advice, sent me samples, 

 showing the reddish and rotten appearance already alluded to. 



