584 



THE UPPER SILURIAN. 



specimen of the reddish variety, containing small scattered crystals of 

 specular iron, gave on analysis — 



Peroxide of iron . . . 33*0 . 





o 







99-7 



With this mineral is found a variety of Spathose Iron, or sparry 

 carbonate of iron, containing about 20 per cent, of carbonate of mag- 

 nesia. It is of a light yellow colour, and runs in little veins through 

 the Ankerite. I have no doubt that all these substances have been 

 molten by heat, and injected from beneath into the irregular fissure in 

 which they are now found. The ochrey red ore, previously mentioned, 

 appears to be a result of the subsequent action of heat on the spathose 

 iron. The ankerite and spathose iron may become valuable for 

 mixing with the other ores, affording lime for a flux and much iron. 



5. Yellow Ochrey Iron Ore. This is found in great quantity on 

 the surface of the vein, and has resulted from the rusting of the 

 ankerite, which soon becomes covered with a yellow rusty coat when 

 exposed. The yellow ochre is a peroxide of iron combined with water, 

 and when calcined it affords a good red pigment. On analysis, it 

 gave — 



Peroxide of iron . . . 74 - 52 

 Alumina .... 4*48 



Carbonate of lime and magnesia '40 

 Silica and silicates . . 6*20 



Water, mostly combined . 14-40 



10000 



6. Brown Hematite occurs in large balls along the outcrop of the 

 vein. It has been produced by the solvent action of acid water on 

 the carbonate of iron, and the subsequent precipitation of iron from 

 these solutions. It is a valuable ore, but is probably most abundant 

 near the surface of the vein. 



