260 A VISIT TO THE PROVINCES 



will surrender the entire earnings of a month, or even a greater sum, if it can be obtained in 

 advance, to secure a companion from prison. 



Under the orders of the proprietor, the direction of the work is confided to an administrador, 

 usually a man of experience, whose salary is in proportion to the extent and productiveness of. 

 the mine, and ranges from $800 to $3,000 per annum. Though few, if any, possess the least 

 acquaintance with geology or theoretical mineralogy, they are men of great observation and 

 practical knowledge. Should the mine have several shareholders, the duty of supervision and 

 instruction is performed by each proprietor in turn. Besides the classes of operatives named, 

 there are blacksmiths, water-carriers, and mayordomos the general duty of the last being to see 

 that the metal be not abstracted during the process of breaking up. Their pay is from $300 to 

 $600 per year. 



In the Annales des Mines, Vol. IX, Prof. Domeyko gives the following geological description 

 of El Bolaco : "The whole hill of Chanarcillo is composed of calcareous rocks, more or less argil- 

 laceous, compact, or earthy; some dolomitic, others containing only traces of magnesia. Sand- 

 stone is not seen, nor schist, properly so called; neither are there conglomerates, nor rocks of 

 crystalline structure. The entire mountain is formed in regular and nearly horizontal strata, 

 slightly dipping to the west in concordant stratification. The aspect of the formation announces 

 a period of tranquillity and continuity of acting causes. 



"The argil of these rocks is composed of two distinct parts, of which one is white, and not acted 

 on by acids; the other a hydro-silicate of alumina and iron, which may be acted on the silicate 

 being soluble in a solution of potassium. It is wholly to the very variable proportions of this 

 argil that are due the different aspects of the rock its compactness and fracture and which, 

 probably, more than anything else, influences the richness of the mines traversing it. 



"The more or less blue color of the rocks is not due to bitumen, but to a silicate of the pro- 

 toxide of iron, which they contain. When boiled with muriatic acid, they also leave a white 

 residuum. 



" I found no organic remains in any part of the mountain which contained metallic veins, 

 although, as I have said, they have been found along the road to the eastward, and near to 

 Molle, as well as along the northwest road, in the environs of Ingenio. Nevertheless, I am 

 assured that an ammonite was found in a rock of the mine lieventon Colorado at many yards 

 below the surface. 



" It is about three hundred metres in a vertical line from the summit of the plateau to the 

 bottom of the lowest worked mine on this mountain, and we can distinguish three parts or 

 stages in this thickness of the formation. We commence with the uppermost. 



" The plateau at the top is composed of a stratum whose thickness varies with the inequality 

 of the surface, but which on the northeast side is from twenty-five to thirty metres. It is 

 composed of marly dolomitic rock, containing more than two thirds of its weight of argil ; its 

 color a yellowish gray, and its fracture a plane covered with dendrites. The whole rock is found 

 completely fissured, and often full of cavities and hollows produced by the fracturing. The 

 surfaces of the fissures, as also those of the cavities, are covered with small bright crystals of 

 spathic lime. The cavities are also found filled with angular fragments of the same rock, 

 each fragment covered on all sides with the same crystalline crust perceptible on the walls of 

 the cavities. On the eastern slope of the same plateau, a part of the stratum is so fractured 

 that it resembles a succession of enormous angular blocks of the same rock, whose interstices 

 are often filled with marly matter pulverulent as chalk, and mixed with small stones of the 

 same stratum. The pulverulent material gave the following analysis: 



Carbonate of lime , 0.335 



Carbonate of magnesia 0,052 



Alumina and oxide of iron . . 0.101 



Silica soluble in potassium 0.170 



Argil not acted on , 0.270 



Water and loss . , . , . 0.072 =-1.000 



