uS Of the Copper 



ciently extenfive, fully to anfwer this queftion, 

 a great deal of attention and caution being requifite 

 in forming a proper judgment on the cafe. 



Now, as to the copper-yield in each fort of pyrites \ 

 whether denominated copper-pyrites, or copper- or es 9 

 I have in various ways attempted to difcover it, 

 without leaving concealed the fmalleft fhare of 

 copper, that happened to be therein. As to thofe 

 that contain much copper, or only a pound the quintal, 

 the method of extracting it is a thing well known: 

 if firft, according to the common way of afTaying, 

 they be brought, in their unroafted ftate, by means 

 of pounded glafs, to crude- ft one-, which crude-ftone % 

 with the ufual dofe of black- flux in a crucible in a 

 wind-furnace may be reduced to black-copper j and 

 this again in the afTay-furnace to rofe-copper ; tho' to 

 procure the copper, on the fcore of its being apt to 

 burn away, from extremely poor copper pyrites^ 

 care and experience are requifite. And, as I have 

 had feveral forts of pyrites from our mines, from 

 which neither I, nor the mod experienced afTayer, 

 could extract the lead copper, I have djfeovered 

 other ways to anfwer the purpofe. The colour I 

 found to be fallacious ; and even extremely pale 

 copper-ores to be rich in copper, this palenefs arifing 

 from the defect of fulphur, and the over- dofe of 

 arfenic. 



Thefe poor copper-pyrites 1 tried both in their 

 crude and roafted (late, nay even in their iron-re- 

 gulus, with vinegar, alio Ipirit of fal-ammoniac •, 

 as thefe are fharp waters, which copper readily yields 

 to ; but without the copper giving forth its green 

 and blue colours, on account of their being entirely 

 defended by the iron : and when any green call 

 happened to manifeft idelf, it was owing to a coppery 



iron» 



