192 Mr, Field y on the Mineral Treasures of the Andes, [Feb. 3? 



rarer, being generally associated with sulphate of lime in intimate 

 mechanical union. The " Cobre Aiiilado" of the mines is a soft 

 indigo-blue coloured mineral, which by long digestion in water loser 

 its sulphate of lime, the residue consisting of tolerably pure proto- 

 sulphide (Cu S). Immense masses of what is usually termed blue 

 sulphide of copper, but which is really a double sulphide of that metal 

 with iron, occur in Tamaga, a district lying between Valparaiso and 

 Coquimbo. The pure mineral contains about 56 of copper, 23 of sul- 

 phur, and 21 of iron. 



The ordinary yellow pyrites (Cuj S, Fca S3) and peacock ore abound 

 throughout the Andes. 



Arsenide of Copper — Domeykite. — This mineral is interesting, 

 being somewhat similar to condurite, analyzed by Mr. Faraday in 1826, 

 and subsequently by Dr. Blyth in 1 848. The compound investigated 

 by these chemists, however, was a mixture of arsenite of copper, in 

 conjunction with the arsenide. Domeykite does not contain arsenious 

 acid, but is simply expressed by the formula Cu 6 As. 



Algodonite contains more copper than the former, and is composed 

 of 12 atoms of copper and one of arsenic. 



Guayacariite. — This mineral, very similar to enargite, is found in only 

 one locality in Chili, very high up in the Cordilleras, the mine being 

 for a great part of the year, quite inaccessible. It consists of 3 Cug 8, 

 As S5, or three atoms of disulphide of copper united to one atom of 

 pentasulphide of arsenic. Arsenic is generally found combined with 

 three atoms of sulphur, when in combination with the sulphides of 

 most metals. The state of pentasulphide in this instance, makes the 

 mineral peculiarly interesting. 



Vanadiate of Copper, in union with vanadiate of lead, exists in the 

 " Mina Grande," near Coquimbo. It has a brownish earthy appear- 

 ance, and contains generally from 13 to 16 per cent, of vanadic acid. 



Silver Minerals. — For a long time the principal, and indeed the 

 only great source of silver in Chili was from the province of Coquimbo, 

 the district in which the mines were situated being about fifty miles 

 distant from the coast. The rich silver mines of Chanarcillo, in 

 Copiapo,were discovered about the year 1835 by Juan Godoy, a wood- 

 cutter. Sleeping on the hill, after a hard day's toil, he kindled a small 

 fire, and in the morning he discovered underneath the embers a bright 

 metallic surface, which he mistook for lead, but which proved to be 

 silver. The locality has yielded enormous riches since that time. 

 Besides native silver, the chloride, two or three varieties of chloro- 

 • bromide, the bromide and iodide have been discovered, as well as the 

 dark and light vosiclers (3 Ag S + S b S3) a (3 Ag S + As S3) the 

 sulphide Ag S, Polybasite, and a variety of other interesting appear- 

 ances. 



Arquerite^ named from Arqueros, the district in which it is found, 

 consists of Ag 6 Hg. For a long time, with the exception of the 

 liquid amalgam discovered by Del Rio, in Mexico, it was considered 

 the only native amalgam of silver. M. Domeyko, to whom the 



