1 2 Report on the Copper ores of the Deoghur Mines. [No. 8. 



to this experiment; and I think 15 might have sufficed, but my first 

 object was to prove the perfect practicability of the Spanish American 

 processes with various ores, and to ascertain the full quantity of silver 

 without reference to the expenditure of the ingredients, which on so 

 small a scale were necessarily used in larger quantities, or of the time, 

 which can only be definitely settled by large experiments also. The 

 result of this trial too was highly favourable, a3 somewhat more than 

 8 grs. of pure silver were obtained ; but taking the produce at 8 grs. 

 this would be for the Caxon of 5000 pounds Avoirdupois, as before, 

 13.5 marcs, and thus above an average ore. 



It will be observed that I have used the Cornish term gossan when 

 speaking of some of these ores, to designate the instances in which the 

 copper ores run into a pale red, earthy ore, which is in fact (as in C.) 

 a Pacos, as it contains a portiou of silver. This word gossan is a term 

 used by the Cornish miners to distinguish exactly an earthy, friable, 

 ferrugino-cupreous earth, which appearing at the surface is held to be 

 an indication of copper below. It is in fact a copper Pacos, but con- 

 tains no silver, and it does not, that I am aware, as some of our speci- 

 mens do, shew itself to be a separate mineral by running in a distinct 

 vein at right angles into, and altering the copper vein where it meets 

 ife Cornish gossan is also friable and full of hollows, like ore in a state 

 of decomposition, which it is generally supposed to be ; ours more 

 resembles a high-coloured but soft brick, except in H. which might be 

 taken for a red iron ore. 



As a good gossan in Cornwall is taken to be an indication of a good 

 copper vein, so the Pacos in Peru, and the Colorados in Mexico, (being 

 the same mineral) are held to be good indications of silver below ; and 

 it is said too that it is rarely found to run deep, that is, not above 50 or 

 1 00 fathoms, changing then to richer ores. Whether this be the case at 

 Beoghur, time and enterprize can only shew us. From analogy one 

 would say there may be something worth sinking a small shaft for, and 

 tracing how far the veins extend on the surface ; and if they crop out at 

 any other part. The Copper and Cupro-Plumbite (K.) may be well 

 worth exportation in their raw state, when simply dressed and picked 

 with care. 



In a geological and mineralogical point of view the discovery of 

 these ores in a country yet so little known to us holds out some hope 



