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CHAP. XL 



Of the Silver in the Pyrites. 



AS to the /liver in the pyrites , it is an un- 

 doubted truth, allowed by every careful af- 

 fayer, and which I myfelf have experienced, that 

 pyrites, as fuch, never holds above half a drachm of 

 filver in the centner. For, tho' fometimes the proofs 

 ihould rife to i, 2, 3, 4, 5, and 6 drachms, as I have 

 often obferved fuch various yields, we are at the fame 

 time to know (1.) That fuch fort of pyrites is com- 

 monly coppery •, and that the copper therein is, if 

 not the caufe, yet the fign of the admixture of 

 other ore. (2.) That fuch yieldy pyrites-mixt- 

 work, or pyrites-meal, has often other veins unob- 

 fervedly interfperfed amongft it, which may great- 

 ly raife and heighten the yield ; and to this fort may 

 be fometimes referred the cubical, marcafitical py- 

 rites, fuch as thofe of PretzfchendorfT, which ap- 

 pear pure and unmixt, tho' internally they make 

 an appearance of being glittery and mock-leady. 

 (3.) That hence the proofs vary much, nay fome- 

 times fo far as to fall fhort of half a drachm. 



The fame thing holds of the white pyrites, 

 namely, the mifspickel, or poifon-pyrites, an half, 

 or a quarter of an ounce may often be procured 

 from them; but a drachm, half a drachm, and next to 

 nothing at all, are generally what the pr ooj ~-fc he 'dule 

 fhows. Yet here, for particular reafons, I muft 

 allow fome filver to the white rather than to the yel- 

 lowifh, or fulphur pyrites: and I have been inform- 

 ed from Sweden, that they have there a mifgickel 



of 



