74 MINERALS OF CHILE. 



together, the interstices being filled with an earthy matter as 

 pulverulent as chalk, and composed of one third carbonate of 

 lime and two thirds clay. It is in these fissures of the upper 

 layer that very considerable masses of chloro-bromide of silver 

 have been found. 



The second division of the rocks differs but little in char- 

 acter from the last, being an argillaceous limestone ; it is, 

 however, more regular and not so much fissured ; at the same 

 time the metalliferous veins traversing it are much poorer. 

 The thickness of this division is over three hundred and twenty 

 feet ; and here commences the third division, where the lime- 

 stone contains less clay and but a little trace of magnesia. The 

 color of the rock is a bluish-graj^ mottled with yellow; of a 

 compact structure and conchoidal fracture. This rock contains 

 the principal wealth of the Chaiiarcillo mines, and in it seems 

 to be the principal deposit of chloro-bromide of silver. The 

 thickness of this bed is estimated at nearly four hundred feet. 

 Below this again lies another bed, where the calcareous rock 

 is again more argillaceous and the veins poorer. In this por- 

 tion of the mountain porphyritic rocks are found at the lowest 

 depths to which the workings have gone. 



Numerous metalliferous veins traverse this mountain in 

 every direction. The materials constituting these veins (and 

 mixed with which the silver-ores are found) are the carbonates 

 of lime, iron, and magnesia, zinc and manganese, and the sul- 

 phate of baryta, which, however, exists in less quantity in 

 these mines than in those in other parts of Chile. The metal- 

 liferous portions of these veins are composed principally of 

 chloro-bromide of silver mixed with native silver and a small 

 portion of sulphuret and sulpho - arseniuret of silver. The 

 chloro-bromide does not show itself in equal abundance at all 

 depths of the productive calcareous bed already mentioned; it 

 is, particularly in the upper, one or two hundred feet; below 

 this depth the gangue becomes less and less calcareous and the 

 mineral changes its nature. At first it is the pure chloride or 

 little mixed wi'th sulphuret; then the proportions of sulphur, 

 antimony, native arsenic, and ruby-silver commence to increase; 

 so that at three hundred feet depth hardly a trace of chloro- 

 bromide is found, the silver being associated with sulphur, 

 arsenic, and antimony. 



