MINERALOGY. i 5 f 



The variety from Bifpergs Klack 

 has been examined by Mr. Quill, 

 and has, by its volatilifmg under the 

 mufrel, in form of a white fibrous 

 fublimate, induced that gentleman to 

 examine the black lead more parricu- 

 larly - 5 and he has publifhed fomc 

 very remarkable experiments on it in 

 the Tranfaclions of the Academy of 

 Sciences at Stockholm, for the year 



1754. 



l\ Of a fteel-grained and dull texture, 



Tex turd chalybed. It is naturally black, 

 but when rubbed it gives a dark ^ead 

 colour. 

 c. Of a fine fcalv and coarfe-grained 

 texture, Tex turd micaced 13 granu- 

 lata, Coarfe Black Lead. 



It has at the fame time a fcaly and 

 a granulated appearance. 



From Gran in the province of 

 Upland, and from Tavaftehuflan in 

 Finland *. 



* ProfefTor Pott has examined the black lead in covered 

 veflels, and Mr. Qnift in an open fire, from which difference 

 in the method of treating it, different notions have arofe : be- 

 caufe the black lead is nearly unalterable when expofed to 

 the fire in covered veffels, or when immediately put into a 

 ftrcng charcoal fire, but it is almoft wholly volatile in a cal- 

 cining heat. This is the cafe with feverat others of the mi- 

 neral phiogiftons ; and from this we may in general <earn, how 

 neceff^ry it is to examine the mineral bodies by many and 

 different methods, and to endeavour to multiply the experi- 

 ments more than what has been hitherto done. Pencils are 

 made from the black lead ; as alfo the black lead crucibles. 



SECT, 



