Elements of Mineralogy. 



SPECIES XVIII. 

 Mineralized by Sulphur, Arfenic and BtfmutB. 



35. Such ores have been talked of, but 

 their exiftence has not as yet been proved. 



36. Silver has alfobeen found in the fulphu- 

 fated ore of zinc called pech blend, and in that 

 of lead called galena, particularly the latter, 

 alfo in the copper pyrites, but in fmall quan- 

 tity, as fhall be mentioned in their proper 

 places. 



37. If an ore yields I per cent of filver, it 

 is generally worth extracting. 



CHAP. IV. 



Copper. 



I. Its colour is pale red as is well known. 

 Its fpecific gravity from 8,7 to 9,300, de- 

 pending not only on its .purity, but alfo on 

 its condenfation, by hammering. It is foluble 

 not only in acids, but alfo in alkalis and neu- 

 tral falts. It is precipitable from moft acids, 

 in its metallic form, by a clean plate of 

 iron, and moft of its acid folutions are con- 

 vertible into a deep blue, by volatil alkalis. 

 Thefe characters are fufficient to diftin- 

 guifh it. 



SPECIES. L 



