Oruro is next to Potosí in production of silver, and in tin it stands first. The richest silver ores, as at Huanchaca, are so exported, the poorer are treated on the spot. Other rich mines are well known.
Tin mining is a more recent industry, dating from 1895. Already it has become the leading export of the country, which now provides more than one-third of the world’s supply. It was well known to the Spanish colonists as much of it was mingled with the silver, but they rejected it as rubbish, using it to fill in depressions. Large profits have been recovered from these fillings and from the dumps. While tin is produced in many other parts of the world, the Bolivian lodes are of unusual extent and richness. Their production is now exceeded only by that of the Straits Settlements. Since the development of the tin plate industry and its use in other ways the demand for tin and the price have enormously increased; from $350 a ton in 1898 to $900 before the war. In 1912 tin was produced, barilla, 60 per cent pure, 37,700 tons, worth $18,000,000; in 1918 the value of tin exported was $45,364,000.
All along the eastern part of the plateau from Lake Titicaca to the southern boundary, tin is found in thick unbroken lodes. The three principal districts are La Paz, Oruro, Potosí. In La Paz the best known mines are on the slopes of the splendid mountain, Huaina Potosí in the Cordillera Real, though many other mines are worked. Those in the Department of Oruro are more important, producing one-third of the output. The lodes vary in thickness from a few inches to 10, 15, or 20 feet. Rich pockets are found 30-60 feet in diameter, and veins with stannic oxide fragments, running from 50 to 100 per cent. Cassiterite, tin stone, or tin with stannic oxide, is frequent with 55-60 per cent tin; this is sent to Europe as extracted. The percentage of tin in a lode is very variable, often 6-8 per cent, sometimes 15. Veins of tin on the Cerro Potosí penetrate the hill parallel to veins of silver; some are united; in others tin, silver, and copper alternate or are in union. The tin is generally in the upper part nearer the surface. Sulphides are found at Oruro, but oxides are more frequent. All are at an altitude of about 10,000-17,000 feet. The large Socavón Company employs 1000 hands, has a concentrating plant, and puts out six tons of silver and 250 tons of tin yearly. Many other mines export barilla, some of it with 70 per cent of tin. A Bolivian, Simon J. Patiño, from being an ordinary laborer has risen to be the Tin King, both banker and mine owner, working his mines by modern methods and electric machinery. His mines at Uncia are among the richest in the world, producing about 30 per cent of the Bolivian total. The Llallagua mines, the richest of all, have still greater production.
On Huaina Potosí are placers containing with tin, gold in flakes, bismuth, and oxide of iron; more in other locations. The Company owning the Chlorolque Mountain and other properties, with tin as the principal product, mines also silver, bismuth, copper, and wolfram; it paid a 30 per cent dividend in 1917. Capital only is needed to exploit on a much larger scale these rich and available deposits. Three hundred to four hundred dollars a ton hardly paid the cost of production, but with prices three times as much it is a highly profitable business. The Guggenheims have recently purchased three tin mines located at Caracoles on the Quimsa Cruz Range, south of Illimani, to which they have built an automobile road 150 miles from Eucalyptus, a station on the main line between La Paz and Oruro. The mines are at an altitude of 16,000 to 18,000 feet, the quarters at 15,000 to 16,000. The tin runs to 10-15 per cent. It is thought that the property will rival the Uncia. The International Mining Company has a tin property in the Yungas Province 52 miles from La Paz at a height of 8000 feet, a rather more comfortable altitude.
Copper. Of late the copper deposits in Peru and Chile have received more attention than those of Bolivia, but this country also has extensive formations from Lipez at the south where white copper is found, along the East Cordillera, past Potosí and Oruro to Corocoro in the West, ending in the Nudo of Apolobamba. Veins occur in all the buttresses of the Andes.
Copper is found chiefly in its native state, the deposits of Corocoro being especially famous. The copper here occurs in powder, plates, or nodules, in beds of reddish sandstone. One veta, or mineralized bed, is 1000 yards deep, extending several miles; another, a branch formation above this surrounds it on the southwest and east, occupying a great part of the Desaguadero Valley. Both formations are arseniates. One branch 2000 yards thick extends 6 miles; in another direction a branch runs 35 miles from Corocoro to Chacarilla, then branching south and east. Copper generally occurs in small irregular grains with from 70 to 92 per cent copper. The native copper, the great wealth of the mines, here ranges from microscopic grains to plates and arborescent forms called charquis. At La Charcarilla large plates are found 3¹⁄₂ inches thick. Ores with 15-20 per cent copper are usually neglected. As there are no good kilns, barilla is exported 80 per cent pure, a quintal, 220 pounds, costing $3-4 for production. Except from Corocoro the present output is insignificant. For a time these mines were abandoned owing to the low price of copper and the difficulty of transport. It was formerly necessary to send the barilla by carts, mules, or llamas to the port of Arica, or else to the Desaguadero River, to be carried in boats to Lake Titicaca and Puno, thence by rail to Mollendo. With the great increase in the price of copper and the opening of the Arica-La Paz Railway with a 5 mile branch to Corocoro, these difficulties were removed and active work progressed with a broad field for enlargement. Copper formation here is said to resemble greatly those in Northern Michigan, such as the Copper Range, and the Calumet and Hecla. In 1917 over 82,000,000 pounds were exported, worth above $4,000,000.
Lead is found in the region of La Quiaca and some is exported by way of Argentina. Galena, an ore of lead and silver, is widespread.
Bismuth. Of less used minerals bismuth may be mentioned, in the production of which Bolivia leads the world and controls the supply. At present, chiefly used as a drug on account of its high price, it might be more largely employed in alloys. Bismuth ore, as carbonates, oxides, and arsenical sulphates, is so abundant in many parts of Bolivia that if bismuth sold at 20 cents a pound a fair profit would be realized. With the price for years $3500 a ton, it would seem a profitable business to engage in. Over one million pounds were exported in 1918 worth one and a half million dollars.
Antimony also is found in large quantities. Nearly 18,000 tons were exported in 1916, worth approximately $5,000,000, but with high prices and abnormal demand due to the war. Less than one per cent of the quantity was exported in 1912. The ores are rich, often running 70 per cent pure metal.
Zinc in the form of sulphides or blends is abundant, largely in connection with silver. Such ores are sent to Europe, there to be separated, the scarcity and almost prohibitive price of coal rendering such a course desirable for various products, to avoid the excessive cost of smelting; at the same time the high cost of transportation limits the export.