Of the Silver, &c. 213, 



of four ounces in fikutx-yidi \ though it maybe 

 queried, whether fuch be a pure mifspickel, and not 

 rather a fmalt-cobald, thele being often not cafily 

 diftinguifhable, and generally filvery. But here 

 again I find, even a mifs picket ', that breaks in a- 

 mongft the noble ft veins, tho' rarely, to be no 

 move filvery than another from coarie veins. 



But when the pyrites is coppery, as from the 

 copper- yield we may fufpect the coclion of fome 

 other ore and metal, we may then rather hope for 

 filver, tho* not conftantly, not indeed as an effen- 

 tial, but as an incidental part of the pyrites, in the 

 fame manner as copper itlelf is fo. Nay, this in- 

 cidentally of the filver in copper-pyrites is itill fo un- 

 certain, that there is no measuring or proportioning 

 the yield of thtfuver, as might be imagined, by 

 that of the copper. But there are copper-pyrites, 

 very rich in copper, which neverthelefsdo not yield 

 the more filver, nay fometimes yield lefs than 

 thofe that are poorer in copper. And here we mud 

 be upon our guard againft being impofed upon by 

 names given to pyrites, either from the colour, the 

 filver-vein, where they break, or their ufe in fmelt- 

 ing for filver. 



Thu:, from Norway, I have had, under the 

 title of a filver -pyrites, a barren ftone or rock, 

 confiding of fmall, tender layers of quartz and 

 glimmer interchangeably, with foils or ipangles of 

 filver upon it, where it had been broke off. Now, 

 not to mention, that we are not careful enough ro 

 diftinguifh pyrites from flint or quartz, which this 

 ftone really was, I (hall here only obferve, how far- 

 fetched fuch denominations often are, which point 

 not at the effence, but accidents of things ; as fuch 

 pretended filver-pyrites hold no filver of themfelves, 



F 3 but 



