from the Pyrites^ 297 



remarkable difference, that the yellow give not at 

 all, or with difficulty, at the day, but, in the groove 

 very readily : for, having in various manners endea- 

 voured to vitriolife the copper-pyrites j or the yel- 

 low copper-ore, and for that end expofed it in nu- 

 merous ways, and in different places, both whole, 

 and beat fmall, alfo in pretty large heap-work, both 

 naked and covered, I could never procure any vi- 

 triol, though after an expofureof many years ; ne- 

 verthelefs, I would not pronounce the thing impof- 

 fible, though very difficult : and therefore I would 

 thus diftinguifh the fpontaneous vitriolifation of py- 

 rites, and affirm the yeliowifh to be fubject thereto, 

 both above and under the earth ; the yellow only 

 under, and with the greateft difficulty, above the 

 earth. The reafon of this different efficacy of the 

 air depends doubtlefs on incidental circumftances, 

 into which we are unable, with all our art, to bring 

 the yellow pyrites. 



Now, it is a difficult matter to affign either a 

 general or particular reafon, why for each fort of 

 pyritce, the vitriol' fation happens either flow or 

 quick, or not at all : for, though the copper great- 

 ly (lands in the way of vitriolifation, yet there 'are 

 circumftances and examples, wherein this docs not 

 always hold good •, as I have had yeliowifh pyrites 

 that contained no copper, and yet (hooting with 

 great difficulty, nay often not at all, into vitriol\ 

 of which we have many in fiances here at Friberg 

 under the appellation cobald, or a fulphureous, ar- 

 fc:.icz\ pyrites. There are two forts of pyrites, the 

 one from Pretzchendorff, the other from the Ehroe- 

 Schlange , the latter of which vitriolifes, but tht 

 former not in the lead, and yet they entirely agree 

 in their fmali copper-yield. But what is mod re- 

 markable, there are pyrites, not only agreeing en- 

 tirely 



