Chile saltpetre, cubic nitre or sodium nitrate, NaNO,, occurs under the same conditions as ordinary saltpetre in deposits covering immense areas in South America, which are known locally as caliche or terra salitrosa, and abound especially in the provinces of Tarapaca and Antofagasta in Chile.
It was formerly capital of the Bolivian department of Atacama and the only port possessed by Bolivia, but the seizure of that department in 1879 by Chile and the construction of the Antofagasta and Oruro railway deprived it of all importance, and its population, estimated at 6000 in 1858, has fallen to less than 500.
Like the other provinces of this region, Antofagasta produces for export copper, silver, silver ores, lead, nitrate of soda, borax and salt.
One of these, running from Antofagasta to the Caracoles district, was afterwards extended to Oruro, Bolivia, and has become a commercial route of international importance, with a total length of 574 m., 224 of which are in Chile.
Extensive deposits of the salt (called caliche in its crude, impure state) in the provinces of Tacna, Tarapaca, Antofagasta and Atacama owe their existence to the rainless character of the climate.
Among the smaller towns prominent because of an industry or commercial position, may be mentioned the Huanchaca mining centre of Pulacayo (pop. 6512), where 3200 men are employed in the mines and surface works of this great silver mining company; Uyuni (pop. 1587), the junction of the Pulacayo branch with the Antofagasta and Oruro railway, and also the converging point for several important highways and projected railways; and Tupiza (pop. 1644), a commercial and mining centre near the Argentine frontier, and the terminus of the Argentine railway extension into Bolivia.
Gold is found in nearly all the provinces from Antofagasta to Concepcion, and in Llanquihue, Chiloe and Magallanes territory, but the output is not large.