| Besides Australia , the state of “Piaui” in northeastern Brazil is the
only place where gem-quality precious opal has been mined in commercial
quantities. The deposits are located within a radius of 20 kilometers surrounding the town of “Pedro Segundo”. The “Boi Morto”-mine and parts of the “Roca”-area are primary deposits. At Boi Morto the samples are found at a sandstone quartz-dolerite contact. Because of its size and frequent involvement of foreigners, Boi Morto has always attracted most public attention, in Brazil and abroad. But during the last 20 years, 95 % of all opal in Pedro Segundo were processed by local people working the alluvial or secondary deposits. In contrast to some of the stones from the primary deposits the alluvial opals show no sign of crazing. This is most likely due to its very low water-content. The samples are translucent to transparent and characterized as white or light opals. They can show a large variety of colors, including reddish, orangey, yellowish and greenish hues. Much of the material has a very distinct layered structure contributing to its body-color and play-of color. The standard gemological properties correspond to the known ranges for opal. Although the opals found in Pedro Segundo are of high quality, today the commercial significance of these occurrences is minimal. The low production is due to the harsh mining conditions and the lack of profitability of the alluvial deposits in particular. Unlike many other mining areas, Pedro Segundo is a natural grown community with a 152 year old town record. Its base is agriculture and although drought and famine hit the region every couple of years, the average landowner will not sacrifice his generation-old family farmland to modern mechanical mining and its devastating after-effects. He might allow his friends or relatives to try their luck, who would then form groups of three to five people and spend part of their spare-time (mostly during the dry season from may to december) looking for opals with a shovel and a sieve. But where erosion has dispersed the few existing gems during hundred of thousands of years, nobody can expect an easy profit. All this creates a rather picturesque mining environment. For futher information have a look at: http://www.gemfilmchannel.org or contact e-mail: brasilopal@hotmail.com |