REPOSITORIES OF METALLIC ORES. 



299 



es of native copper of many thousand pounds weight, are said to be 

 found on the surface, in the interior of North America. 



Iron in every kind of rock. 



Tin, in granite, gneiss, mica-slate, and slate. 



Lead and zinc, in primary and transition rocks, except trap and 

 serpentine ; in porphyry and sienite ; in the lowest sandstone, and 

 occasionally in coal strata. 



Antimony in primary and transition mountains, except trap and 

 serpentine; it is also found in porphyry and sienite. 



Nickel, bismuth, cobalt, in primary mountains, except limestone, 

 trap, and serpentine. Cobalt and nickel also occur in transition 

 mountains, and in sandstone. 



Arsenic, in primary and transition mountains, and in porphyry. 



Manganese, in primary and transition mountains, and occasionally 

 in the lower stratified rocks. 



Molybdena and tungsten, uranium, and titanium, in granite, gneiss, 

 mica-slate, and slate. The latter metals, with chromium, columbi- 

 urn, cerium, and tellurium, are very rare in nature, and can only be 

 reduced to the metallic state with great difficulty. 



