07 ATACAMA AND COQUIMBO. 285 



On the line of contact of the granitic and stratified formations, three leagues 8.E. of Carriso, 

 is the isolated hill omtjiiiiing the silver mines of Agua Amarga. Its external aspect bean 

 strung irsrmUano' t< Kl l'."lar<>, though it is more extensive. From N.W. to S.E. its length 

 is uhotit -l.\ miles, its elevation ahove the sea -l,7.")(l 1'eet, and .ver the MiiT.iijiilin-_' j.lain l.iiin) 

 feet. Min. Tal \eins crop out almost at its very summit. Four diil'en -nt stages or strata are 

 notable in its strut 'hire above the granite forming its base: 1. A formation impregnated with 

 rarlmnate of lime, resemhling compact euritic or felspathic rocks. 2. Blackish-grey porphyry, 

 with small crystals of felspar and amphibolc. 3. Compact calcareous layers, more or less argil- 

 lareous. 4. A stratum of compact blackened porphyry, from six to eight feet thick, which caps 

 the most elevated crest of its southern extremity. More than two hundred metallic veins have 

 been found a number exceeding those at Chafiarcillo ; but as they are nearly vertical, they 

 have not so great a horizontal length as in that district. They vary from an inch to three feet in 

 width, with a general direction north and south, though some few lie N.E. and S.W. Six of 

 them had been famous in their day, yielding abundance of chloro-bromide ores; but at the time 

 of Prof. Domeyko's visit more than 200 mines had been abandoned, a great number of the 

 miners' houses were in ruins, and there remained only a few huts, with about twenty operatives, 

 who found occupation principally as gleaners from the previously rejected ores. There was still 

 one mine yielding chlorated ores lucratively. It was at the very foot of the hill; and though it 

 had been worked to a depth of 120 feet, the granite formation had not been encountered a 

 fact which proves, Prof. Domeyko says, "that the granite wall rises at nearly a vertical angle, 

 instead of forming a horizontal bed under the rocks cropping out at the base of the hill." 



Less than a mile S.E. of the last are the mines of Canas and Rincon de Tunas ; and 

 half a mile S.S.W. of the latter are those of Tunas, which, in their day, afforded as much 

 metal, in proportion to their number, as those of Agua Amarga. Like it, nearly all the 

 veins have been abandoned, and only four remain in operation. Their riches also existed near 

 the surface, some $400,000, principally of native and ruby silver, associated with native arsenic 

 and arsenio-sulphurets, having been extracted within the first fifty feet of the surface. Below 

 that they became sterile. 



One of the most valuable copper districts is Los Camerones, distant in a westerly direction 

 from Agua Amarga about two miles. The vein, enclosed between dioritic rocks composed 

 of white felspar and black amphibole, lies iii a N.W. and S.E. direction, and crops out on the 

 southern face of the hill for nearly half a mile. In this length it is often separated into two 

 parts, the insterstices being filled with rocks of the same character. It is observed that the 

 products from the divided vein are of unequal richness, the ratio of per-centage increasing in 

 one as it diminishes in the other lying in the same transverse plane, and that ores extracted at 

 the junction of the two branches contain the most metal. Carbonates, silicates, and oxides, exist 

 near the surface ; pyritous and purple copper lower in the fissure. The gangues of the oxides 

 are charged with ferriferous argils and micaceous iron. Those of the sulphurets are more 

 quartzy, and also contain much tremolite. Having been opened at the close of the last cen- 

 tury, this is one of the oldest-worked mines of the province. As many of the ores afforded 

 quite fifty per cent. , although the price of copper was scarcely one third as much as at the 

 present day, and there was no market for it nearer than Lima or Buenos Ayres, its proprietor 

 died wealthy. Since then it has been purchased by an English company, who annually extract 

 about 1,200 tons of ores, containing an average of 15 to 20 per cent, of copper. Those which 

 will yield more than 24 per cent, are shipped to England ; 7 to 8 per cent, are rejected; and the 

 remainder are smelted on the spot. For this purpose several reverberatory furnaces have been 

 erected, and the arborescent cacti and branches of shrubs collected in the vicinity afford a 

 scanty supply of fuel. 



Of several other mines in the province which yield small quantities of gold from veins and 

 washings, argentiferous and other copper ores, we only know the names and localities. These 



