MODE mi. ARGILLACEOUS GLlfTENITE. 



of the rubbish of other rocks ? The fracture is 

 also different; and three specimens of various 

 fineness, which I received from Daubuisson at 

 Paris, could never be confounded with clay slate. 



" This rock is uncommonly productive of me- 

 tals, not only in beds but also in veins, which 

 latter are frequently of great magnitude. Thus 

 almost the whole of the mines in the Hartz are 

 situated in greywack. These mines afford prin- 

 cipally argentiferous lead-glance, which is usually 

 accompanied with blend, fahl ore, black silver 

 ore, and copper pyrites. A more particular ex- 

 amination discloses several distinct venigenous 

 formations that traverse the mountains of the 

 Hartz. The greywack of the Saxon Erzgebirge, 

 of the Rhine at Rheinbreidenbach, Andernach, 

 &c., of Leogang in Salzburg, is rich in ores, par- 

 ticularly those of lead and copper. At Voros- 

 patak and Facebay, in Transylvania, the greywack 

 is traversed by numerous small veins of gold. 



" The whole of the important lead-glance form- 

 ation of Leadhills and Wanlockhead is situated in 

 greywack. 



u It was for a long time supposed that this rock 

 was peculiar to the Hartz, where it occurs in great 

 quantity : later investigations however have shown, 

 that it is widely and abundantly distributed. Be- 

 sides the Hartz, it occurs also in the Electorate 



