Chap. 34.] Natural Hiftcry of Sifoer. 217 



and was found, on examination, to confift of- filver 

 united to fulphur. 



Silver is often found in its native ftate, and may be 

 known by its brilliancy and ductility. It is fometimes 

 met v/ith in irregular maflfes, fometimes in the form 

 of capillary threads or fibres, and fometimes in that of 

 branches, formed by octahedrons inferted one into 

 the other. It is alfo often difperftrd in a quartzofe 

 gangue*. 'Native filver is fometimes found alloyed 

 with gold, copper, iron, or regulus of antimony } but 

 native gold much oftener contains filver than native 

 filver does gold. Silver is not naturally found in the 

 ftate of x:alx. 



The vitreous ore of filver is compofed of that metal 

 and fulphur. It is the richeft of the filver ores, and 

 yiejds from feventy to eighty pounds of the metal in 

 the hundred weight. It is of a blackifh grey colour, 

 refembling lead; fome fpecimens are brown, greenifh, 

 yellow, &c. ; it may be cut with a knife, and is fome- 

 times cryftallized. If it is expofed to a heat not fuf- 

 ficient to melt it, the fuphur is difllpated, and the vir- 

 gin filver is obtained in fibres. 



The red filver ore contains arfenic as well as ful- 

 phur. It is a heavy mining fubflance, fometimes tranf- 

 parent, fometimes opake, but commonly cryftallized. 

 It is often of a deep red colour on the outfide, but ap- 

 pears paler within. It affords about half its weight of 

 filver. If it is expofed to a fire carefully managed, 

 and capable of igniting it, the filver is reduced, and 

 forms capillary fibres, fimilar to native filver. 



Tnere is a filver ore containing arfenic, cobalt, and 

 iron, mineralized by fulphur. This ore fometimes 



* A quartzoze or fparry cryftallization, often found inclofing 

 the ores of metals, and therefore called the matrix or rider. 



yields 



