212 ON THE PIRITE OF FRANCE. 



VI. 



On Piritc found in France by M. Cocq, CommiJJary of Gun- 

 powder and Saltpetre Works at Clermont- Fer rant, 'cviih an 

 Analyfisof this Subjiance. By J. J. Drappier, Teacher of 

 Chemijiry at the Polytechnic School,* 



Cryftalsofpi- -M.. COCQ foiind the cryftals of plrlte, in a porous grey 



rite found in the porphyry, with a bafe of feldfpath, and containing cryftals of 



de Dome "^ quartz, forming a part of that chain of primitive mountains 



which fupport the volcanoes of the diftridt of Puy-de-Dome, 



Thefe cryftals of pirite feparate from the rock, and leave in 



the porphyry an impreflion perfe6tly fmooth. 



He alfo found at the village of St. Avit, and in the vicinity 

 of Pont-Gibaud, a fubftance which appeared to be pirite ; in 

 both fitiiations it was fo indeterminate as to render it impoffible 

 —and on the *o pronounce exa6lly on its nature. But in returning to 

 yf/iy to Menat. Menat, at twelve leagues to the north of Clermont, he per- 

 ceived the granites refuming the fame appearance of thofe 

 which he had obferved near Saint Avit and Pont-Gibaud, 

 fometimes the colour of the feldfpath inclined to purple, and 

 oftentimes this fubftance appearing alone in the mafs of the 

 granite, exhibited a beautiful purple. 



The grey porous granite appeared again at intervals, with 

 the appearance of the cryftals obferved in the fame rock near 

 St. Avit and Pont-Gibaud; at laft, after a great many fearches, 

 he found the pirite well defined, and aflliming a chara(5ler 

 much more determinate than that of Scheenberg. 



Its Phyfical CharaSteriJiics. 



Each cryftal is ^^^ colour is a greenifli or blackifli brown. Its form is a re- 

 aprifm of twelve gular hexhedral prifm, of which all the lateral edges are trun- 

 stackiflior cated, which conftitutes it a prifm of twelve faces. Some- 

 greenirh browi^, times the prifm has alfo a fmall face at each of the angles of 

 with a fmooth jf, j^gj-g^ which has not hitherto been remarked in the pirite 

 of Saxony. 



Thefurface of the cryftals is fmooth, and a llttje brilliant: 

 in its interior, the pirite is dull, containing at times forae par- 

 ticles of mica. 



* Journal des Mines, Vol- XVil. p.^OT. 



