The mineral exports are surprisingly small. Gold was discovered by the Portuguese soon after their settlement of the coast in the 16th century, but the washings were poor and attracted little attention. The richer deposits of Minas Geraes were discovered about 1693, and those of Matto Grosso early in the following century. Abandoned placer mines are to be found in every part of the unsettled interior, showing how thoroughly it had been explored by gold-hunters in those early days. Some good mines, like Morro Velho and the abandoned Gongo Soco, have been developed in Minas Geraes, but the great majority are small and not very productive. Diamonds were discovered in Minas Geraes, near the town now called Diamantina, during the first half of the 18th century, the dates given ranging from 1725 to 1746, but the productiveness of the district has greatly decreased. Diamonds have also been found in Bahia, Goyaz and Paraná. Other precious stones found in Brazil are the topaz, ruby aquamarine, tourmaline, chrysoberyl, garnet and amethyst. Among the minerals are silver, platinum, copper, iron, lead, manganese, chromium, quicksilver, bismuth, arsenic and antimony, of which only iron and manganese have been regularly mined. The copper deposits of Minas Geraes are said to be promising. Manganese is mined in Minas Geraes for export. Iron ores have been found in most of the states, and are especially abundant in Minas Geraes. The Ypanema mine and ironworks, near Sorocaba, São Paulo, which belong to the national government, have been in operation since 1810 and small charcoal forges were in operation in colonial times and supplied the mines with a considerable part of the iron needed by them. Many of the richer deposits have never been developed because of a lack of fuel and limestone. Bituminous coal of an inferior quality is mined to a limited extent in Rio Grande do Sul, and another mine has been opened in Santa Catharina. These coal deposits extend from Rio Grande do Sul north into the state of São Paulo. Salt, which does not figure in the list of exports, is produced along the coast between Pernambuco and Cape St Roque. The annual production is about 240,000 tons.
To illustrate the comparative productiveness and relationship of these sources of national wealth and industry, the following official returns of export for the years 1905 and 1906 are arranged in the four general classes previously discussed, the values being in Brazilian gold milreis, worth 2s. 3d. or 54.6 cents to the milreis:--