MINERALS OF CHILE. 73 



traverse compact 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 com- 

 posed 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 G-arin and Pampa Larga mines are the only two excep- 

 tions pointed out to the general law first mentioned. 



The best method of furnishing a correct idea of the miner- 

 alogical 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 are those in the Cha- 

 narcillo Mountain, which is from twenty-five to thirty miles in 

 a direct line from the coast. This mountain is composed of cal- 

 careous rocks, more or less argillaceous. Some of the calcareous 

 rocks are dolomitic, while others are without magnesia. The 

 stratification is regular and almost horizontal. The argilla- 

 ceous matter in the rocks are of two kinds — a white clay, and 

 another composed of a silicate of alumina and iron. 



This locality has been thoroughly examined by M. Domeyko, 

 and he finds no organic remains in those parts of the mountain 

 where the metal veins are found. The same geologist has, 

 however, been informed that an ammonite was found in the 

 rock of Eeventon Colorado at some distance beneath the sur- 

 face. In other parts of this mountain organic remains are 

 abundant in the calcareous rocks, especially the Turritella 

 Andii and Terebratulse. 



From the summit of the Chanarcillo Mountain to the lowest 

 workings of the mines is a little less than one thousand feet, 

 and in that space there can be distinguished something like 

 three distinct divisions in the formation of the rocks. 



The plane at the summit of the mountain is composed of a 

 dolomitic rock, having in some places a thickness of one hun- 

 dred feet; it consists of about one third clay. The rock is 

 split in all directions, and the surface of the fissures covered 

 with small crystals of calcareous spar. In some places it is so 

 much split that it looks more like a mass of broken rocks piled 



