248 Elements of Mineralogy, 



thin laminae incruftating other bodies, foun4 

 in quartz, fpar, ftellftein, pyrites, blend, lead 

 ore, cobalt ore, fparry iron ore, fluors, &c. 

 It is very fufible ; its fpecific gravity 5,000 

 or 5,300; its proportion of filver from 10 

 to 30 per cent ? 



20. It is found, though not commonly, 

 in Saxony , Hungary , the Hartz, and St. Marie 

 ait*, Mines. 



21. Mr. Bergman analyfes this ore in the 

 following manner. Having pulverized and 

 weighed a certain portion of it, he attempts 

 its folution in about 1 2 times its weight of 

 dilate nitrous acid : the copper and filver are 

 diflblved, and a white refiduum remains. 

 The filver he precipitates, not with marine 

 acid, for this would unite alfp to the copper, 

 and with the filver form a triple fait, which 

 would alfo fall, but with a clean plate of 

 copper previoufly weighed ; the filver being 

 in its metallic form, may immediately be 

 weighed, and its contents known : the cop- 

 perfhould then be precipitated by aerated mi- 

 neral alkali > 1 94 gr. of this precipitate well 

 dried are equivalent to 100 of copper in its 

 metallic form ; but from this laft, the weight, 

 which the plate of copper loft, muft be fub- 

 grafted. 



22. The 



