NOTES ON" THE MINERALS FOUND NEAR BRISTOL. 



69 



IRON. 



This important metal is usually found as Carbonate^ ferrous 

 and ferric oxides, and silicate. The Carbonate (Fe CO3) is 

 obtained principally from the Coal Measures. It is mixed with 

 clay and limestone, and yields from 22 to 40 per cent, of metallic 

 iron. An average of 30 per cent, would be a very fair one. 

 This "'clay iron stone" varies in colour from a dark slate to 

 nearly black. The latter, or as it is technically called the '"black 

 band " is the most valuable description. It occurs at Kings wood, 

 and other places where the lower coal measures are worked, and 

 furnishes metal of a capital quality, but for some reason or other 

 the amount of Ironstone raised is very small. 



The following are analyses of two selected specimens of clay 

 Ironstone from Kinsfswood : — 



Very pretty crystallized specimens of the Carbonate, partially 

 oxidized, occur near the south buttress of the Suspension Bridge. 

 The crystals are small and lamelliform, interlacing with each 

 other, giving a soft velvet-like appearance. They contain a 

 considerable portion of Calcic Carbonate and Alumina, which 

 have been derived from the rocks themselves. A sample taken 



