258 



J. H. COLLIIfS OX THE &EOLOGr 



origiD. In c we have, I think, the original pyritous schist or 

 mineralized bands of the Palaeozoic slate. 



The following analyses of the pyrites from different parts of the 

 mines will give a very good idea of the composition of the ores as 

 selected for various purposes, as well as of their freedom from vein- 

 stone when well selected. Por comparison I add two analyses (P) 

 from a neighbouring mine where the " banded " structure referred 

 to above is very well marked. 





L. 



M. 



^. 



0. 



P 







Export Calcination 



San 



Filon al 



La Majada. 





ore 



ore 



T/iriTTi iio 



"V"- J. 









1878. 



1880. 



1881. 



XI one. 

 1881. 



Compact. 



Banded 



Sulphur 



48-98 



50-19 



47-25 



50-00 



49-50 



37-00 



Iron 



41-91 



42-86 



42-35 



41-65 



40-60 



33-00 



Copper 



3-06 



2-29 



4-46 



2-25 



3-62 



4-42 



rr 



Lead 



1-471 

 0-62/ 



undeter- 



- r 1-26 

 \0-24 



trace. 







Zinc 



mined. 



trace. 







Copper sulphate . . 



0-12 



0-20 



trace. 



trace. 







Oxide of copper . . 



0-50 



trace. 



trace. 



trace. 







Arsenic 



1-00 



0-92 



0-61 



0-25 



0-49 



0-47 



Antimony 



0-06 



0-10 



trace. 



*k 







Alumina, bismuth, ^ 















manganese, thal- 

 lium, nickel, cobalt, 



. traces. 



traces. 



traces. 



traces. 



traces. 



traces 



lime, andmaguesia. _ 















Silica and insoluble . 



0-28 



trace. 



2-40 



2-62 



2-14 



22-60 



Sulphate of iron . . 



0-50 



trace. 



.... 



.... 



.... 



trace. 



Moisture 



0-65 



0-20 











Oxygen and loss . . 



0-73 



3-24 



1-43 



3-23 







99-88 100-00 100-00 100-00 96'35 97-49 

 Silver from ^ oz. to 1 oz. per ton in all. Gold from 8 to 11 grains per ton*. 



All the above are samples of well-mixed ores. I add opposite 

 a series of analyses of picked specimens, none of them, however, 

 distinctly crystallized. Q, is chalcopyrite, of a good yellow colour, 

 soft ; R is grey ore, with a good grey colour, and rather harder than 

 usual ; S, white pyrites, very light-coloured, a mass of minute 

 crystals, very hard; T is galena, subcrystalliue and normal in 

 appearance ; IJ, lead-mineral, fine-grained, grey, and granular. 



The pyrites- deposits at Rio Tinto are four in number, known 

 respectively as the j^orth lode, the South lode, the San Dionisio 

 lode, and the Yalley lode. Of these, the South lode is that which 

 was worked extensively by the Spanish Government before the 

 mines were taken over by the present Company ; it is now chiefly 

 worked as an open cutting. The thin branches or veins seen at 



* This small proportion of gold has hitherto resisted all efforts to recover it 

 at a profit, except as regards a small portion of the ore treated at AVidnes and 

 in Germany ; yet it is -worthy of remai-k that the terreros at Eio Tinto, which 

 we may take in. round numbers at 5,000,000 tons, contain more than 2| tons of 

 gold, reckoning only 8 gTains to the ton. The quantity of gold raised annually 

 from the pyrites deposits of the Sierra Moi-ena cannot be less than a ton and a 

 half. 



