'266 



MAGNETICAL PYRITES, 



Its obvious or 

 external proper- 

 ties, 



Where found. 



Degrees of 

 magnetifrh. 



Abundantly 

 found in Cacr- 

 narvonihiie. 



This fpecies is known by the name of Magnetical Pyrites, 

 and is called by the Germans Magnet- Kies, or Ferrum minerali- 

 fatum magnetico-pyritaceum. 



It is mod frequently of the colour of bronze, palling to a 

 pale cupreous-red. 



The Iuftre is metallic. 



The fraclure is unequal, and commonly coarfe-^rained, but 

 fometimes imperfectly conchoidal. 



The fragments are amorphous. 



The trace is yellowifh-gray, with fome metallic luftre. 



It is not very hard; but, when (truck with fleel, fparks are 

 produced, although with fome difficulty. 



It is brittle, and is eafily broken. 



This pyrites has been hitherto found only in fome parts of 

 Norway, Silefia, Bavaria, and efpecially at Geier, Meflerfdorf, 

 and Breilenbrunn in Saxony ; but, having received fome fpeci- 

 mens from the Right Hon. Charles Greville, F. R. S. I was 

 itruck with their refemblance to the pyrites of Breitenbrunn, 

 which happened at that time to be in my pofleffion ; and; upon 

 trial, I found that they were magnetical, and agreed with the 

 latter in every particular. Their magnetic power was fuch as 

 ilrongly to affect a well-poized needle, of about three inches in 

 length; a piece of the pyrites, nearly two inches fquare, acted 

 upon the needle at the diftance of four inches. 



The powder (which is blackifn-gray, with but little metallic 

 luflre) is immediately taken up by a common magnet; but the 

 pyrites' does not aft thus on the powder, nor on iron filings, 

 unlefs it has been placed for fome time between magnetical 

 bars; then indeed it acls powerfully, turns the needle completely 

 round, attracts and takes up iron filings, and feems permanently 

 to retain this addition to its original power. 



In the fpecimens which I obtained, the north pole was ge- 

 nerally the ftrongeft. 



This pyrites was found in Wales, about the year 1798, by 

 the Hon. Robert Greville, F. R. S. who fent the fpecimens 

 above defcribed to his brother, the Right Hon. C. Greville, 

 with the following account. 



" It is found in great abundance in Caernarvondiire, near 

 " (he bafeof the mountain called Moel Elion, or probably with 

 " more accuracy Moel ^Elia, and oppofite to the mountain 



" called 



