THE MINERALS OF CHILE. 97 



ting that the P used (as is frequently done) corresponds to I commonly used by American and 

 English chemists, making the formula, as given by Domeyko, Ag I, which formula is sustained 

 by my analyses, as well as those made by M. Domeyko. 

 The results I obtained are as follows : 



Iodine ------ 



Silver ------ 



Chlorine - - _ _ _ 

 Copper ----- 



99.455 99.489 

 The formula Ag. I gives as per-centage — 



Iodine - 53.85 



Silver -------- 46.15 



1. 

 52.834 

 46.521 



2. 



53.109 

 46.380 



trace. 



trace. 



trace. 



trace. 



100.00 



Arquerite. — This mineral is found in great abundance at the mines of Arqueros, near Coquim- 

 bo; in fact, it is the ore of those mines. It is quite like native silver in appearance, with, 

 however, a little more greasy lustre. It is disseminated through a calcareous rock. Several 

 specimens examined furnished different proportions of silver and mercury, the proportions of 

 silver varying from 83 to 92 per cent. Mr. Domeyko, who has had oppoi'tunity of examining 

 a greater variety of specimens, gives it the following fixed composition : 

 Silver -------- 86.49 



Mercury - 13.51 



100.00 



The formula is Ag.° Hg. 



In all likelihood there is a definitely constituted silver amalgam at Arqueros, but in most 

 instances is altered by admixture with native silver. 



Bemarks on the Geology of the Silver Ores. — In speaking of the copper and gold veins, it 

 was remarked, that they traversed the granite and other old unstratified rocks. M. Domeyko 

 thinks that he has established a law in the distribution of the metalliferous veins of Chile. It 

 is, that gold and copper veins, exempt from arsenic, antimony, and silver, abound in the granite 

 rock; while all the silver veins, without reference to the associates of the silver, belong to the 

 stratified rocks ; and also, that the copper veins found in stratified rocks are very frequently 

 argentiferous. M. Crosnier, however, points out two exceptions to this rule in the province of 

 Copiapo — namely, the Pampa Larga and Garin mines. The Pampa Larga veins traverse com- 

 pact feldspar, a portion of which, near the surface, is transformed into kaolin. The upper 

 portion of the vein contains chloride, and sometimes native silver ; but at a certain distance from 

 the surface the entire mass of the vein is composed of compact native arsenic; in which we 

 find, occasionally, sulphuret of antimony, realgar, arsenio-sulphuret of silver, (sometimes in 

 very beautiful transparent crystals;) arsenical pyrites and calcareous spar are also found. 



The Garin and Pampa Larga mines are the only two exceptions pointed out to the general 

 law first mentioned. 



The best method of furnishing a correct idea of the mineralogical and geological relations of 

 the different kinds of silver ores, is to give an account of how they occur in one or two of the 

 principal mines. 



Some of the most remarkable mines arc those in the Chaiiarcillo mountain, which is from 

 25 to 30 miles, in a direct line, from the coast. This mountain is composed of calcareous 

 -IS* 



