TAB. XXX. 



FERRUM sulphureum. 



Sulphuvet of Iron. Pyrites. 



Class 3. Metals. Order 1. Homogeneous. 

 Gin. y. Ivon. Spec. 5. Sulphuret of Iron, 



D'w. 1. Crystallized. 



Spec. Char. Sulphur combined with Iroru 



j. hese crystals were communicated by the Rev. H. 

 Davies, from Parys Mine, Anglesea, where there is great 

 abundance in some places, heaped together like grains of 

 sand, so small that their lustre is lost in their minuteness, 

 much less can the cubic form be seen without a magnifying 

 glass. The rocks of limestone, and those passing to re- 

 gular slate, contain them of different sizes. The vpper 

 figure is from a specimen the gangue of which is between 

 common limestone and slate, and contains no small quan- 

 tity of the crystals. The gangue is in the more chalky 

 parts stained a little green, perhaps from some oxide of 

 copper. The lower figure is a piece of undulated (other- 

 wise common blue) slate, which is a durable sort if free 

 from pyrites, as the common air decomposes the pyrites, 

 decays the iron, and the slate becomes rotten. This will be 

 further explained when we are treating of the best slate of 

 Wales, Westmoreland, Yorkshire, Cornwall, &c. 



