300 Elements of Mineralogy. 



times amorphous. It owes its colour to 

 mixture of copper. 



V. VARIETY* 



Black. 



8. The moft uncommon of all, and oc~ 

 curs either cryftalized, or of an indeterminate 

 form* 



9. Thefe ores, when freed as much as 

 poffible from earthy matter, are eflayed 

 in the moift way, by folution in fpirit of 

 nitre. The folution being boiled, depofits 

 the calx of iron. If the lead be then pre- 

 cipitated by an aerated mineral alkali, 132 gn 

 of the precipitate, will denote 100 of lead in 

 its metallic ftate. If the ore contains copper* 

 it may be feparated by digefting the calx in 

 volatil alkali; if it be fufpedted to contain 

 lilver and copper, then, after the feparation 

 of the copper, the calx fhould be rediffolved 

 in nitrous acid, and both the lead and filver 

 precipitated by the marine acid ; the marine 

 fait of lead is rediflbluble in 30 times its weight 

 of boiling water, but that of filver will 

 remain undiflblved, or that of filver may 

 be feparated by cauftic volatile alkali. 



10. In the dry way, thefe ores are redu- 

 cible by the fimple addition of phlogiftori 

 and fufion. 



SPECIES 



