476 NOTES ON SOME OXIDISED COPPER ORES. 



materially, as it became possible to import coke and to smelt the 

 ores on the spot. At first the ores were sent by rail about 20 

 miles to the southward where a small smelting plant had been 

 established by independent parties, and here about 1000 tons of 

 the ore were smelted with excellent results — thus proving the 

 mines to be of value. As the developments increased a smelting 

 plant consisting of two water-jacket furnaces with all necessary 

 accessories, each capable of treating 40 tons of ore per day, was 

 erected, houses for a considerable number of work-people were 

 built, offices and stores were established, water-tanks constructed, 

 &c. ; and in fact the property now consists of a self-contained 

 mining and smelting establishment, supplied with plant far in 

 advance of its present development and output. 



Description of the Ore-deposits. — The copper-ore seems to be 

 especially associated with the garnet-rock intrusions, the ore 

 either occupying fissures and cavities, or else permeating the 

 whole mass of certain ''beds" of this rock. The copper is 

 always accompanied by calcite, and sometimes by calcareous 

 deposits of a tufaceous nature ; frequently by oxide of iron, and 

 not seldom by considerable veins and masses of barytes. The 

 deposits at the place known as El Promontorio vary from 3 up 

 to 1 2 feet thick, and dip at a low angle directly into the hill. 

 There are several distinct "beds" interstratified with cuprif- 

 erous garnet-rock. This when freest from copper always 

 contains from J up to 1 per cent, but the cupreous beds yield 

 5 up to 50 per cent, of smelting ore, averaging 6 to 10 per cent, 

 of copper — partly as green carbonate lining numerous minute 

 fissures, or as specks, spots, and patches of oxide, carbonate, or 

 sulphide interspersed between the crystalline particles and grains, 

 — the whole series affording a fine example of what is known as 

 selective segregation. In selecting portions of these beds for 

 smelting a great deal of judgment is necessary, since the 

 brilliantly coated green fragments often contain less than 2 per 

 cent of copper, while the red, brown, or purple masses which 

 seem to be very largely composed of cupreous material are at 

 times not much richer. On the other hand certain comparatively 

 light reddish-brown masses are found to run up as high as 20 

 per cent, in copper. The most minute differences, of tint, of 

 solidity, of texture, must be observed in these oxidized outcrops, 



