B. Silliman — Association of Gold with Scheelite in Idaho. 45 



vided material to a conclusion before abandoning the field t< 

 him ; the work however was delayed by other and more im 

 portant researches and it was not until this winter that I wa 

 ready to examine the products of the reaction of sodium 01 

 a mixture of parabromanilin and parabrom toluol ; just as '. 

 had proved the absence of any base other than bromanilin ] 

 received the paper* Ueber e'ine neue Bildung des Azoben 

 zols by E. Anschuetz and Gr. Schultz and guided by it hav< 

 succeeded in detecting also the azobenzol. I can therefore con 

 firm the results recorded in that paper in every particular. 

 To avoid interfering with any of the above-named gentle 



Art. LI. — On an <. 



A correspondent in Idaho has lately sent me a specimen, 

 obtained from a mineral vein, in which native gold is - 

 with scheelite and quartz. ' On account of some resemblance in 

 color to grossular garnet, the miners mistook the scheelite for 

 this species. But the high density of the mass at once attracts 

 attention and a trial for hardness alone proves it is not garnet. 

 The pyrognostic characters also show the absence of - 

 the presence of tungstic acid. The powdered mineral treated 

 with hvdrochloric acid develops at once the characteristic yellow 

 io acid, and zinc converts this solution to the familiar 

 blue of tungstic oxide. . . 



The gold appears in the scheelite, intimately associated with 

 a small amount of pyrite, interspersed in the mass of scheelite 

 and quartz. The pyrite is considerably decomposed, yielding 

 -brown oxide of iron, and some green stains indicate 

 also chalcopyrite, traces of which are detected by close obser- 

 vation. Leucopyrite is also present in minute quantities But 

 the total quantity of sulphides is certainly not over 1 to 1£ per 

 cent of the mass, if so much. 



The scheelite is massive, with few crystalline faces; its color 

 " yellow-brown, resembling chondrodite. Portions of it are 

 ,aHe free from quartz or any mineral but gold. I found the 

 density of the entire mass (weighing 37942 grams) t 



• chondrodite. Portions of i 

 ^TreeTom quartz or any mmendboi goWJt foom^ 



ite =6, and 



mVthe minor constituents of the mass, the proportions 

 of these two minerals is as 270 : 109-37, or 246 parts of quartz 

 to 1 part of scheelite. This is doubtless much above tne aver- 

 * Ber. Deutsch. Chem. Gresellschaft, ix, 1398. 



