Minas Gerias: The Slate Province

   This prominent position was conquered in only 25 years of mining and industrial activities of the Minas Gerais slates, which accounts for 90 of Brazil’s production and almost all of the slate exported to the rest of the world.
   Minas Gerais slate production totals approximately 500 thousand tons per year, resulting in 18 million m² (193 million ft²) of slabs, tiles, billiards, roofing tiles and other products. In 2004, Minas Gerais slates exports reached $56.6 million, with a volume of 175,800 tons. Those exports showed a growth of 45.1 percent from 2003, and already represent 47.6 percent of all of the total dimensional-stone exports of Minas Gerais.
   The Minas Gerais slate industry involves approximately 400 quarrying and processing companies, generating 6,000-7,000 direct jobs. Called the “Slate Province of Minas Gerais,” with an approximate area of 7,000 km², it constitutes the world’s largest known and explored geological reserves of high-quality slates.
   The extraction and processing industry of slate in Minas Gerais is located in the central region of the state, at a medium distance of 150 km from Belo Horizonte. It includes all of the municipal district of Papagaio, and sections of the municipal districts of Caetanópolis, Felixlândia, Pompéu, Paraopeba, Curvelo, Martinho Campos and Leandro Ferreira.
   Approximately 50 companies are involved in quarrying in 28 active areas of extraction. More than 300 companies, mainly of small size, work in processing in the producing municipal districts, making the slate sector one of the principal socioeconomic segments of the region.
   The principal extraction and processing focus is the municipal district of Papagaio, which accounts for some 80 percent of the province’s total production. The main variety is gray slate, followed by green, rust, black and purple. The principal commercial product, involving at least 70 percent of the processing industry, is standardized tile with natural cleft used mainly for flooring and wall coverings.
   Besides the varied chromatic patterns, the slates stand out in interior use for their great aesthetic rapport with wood, metals and carpets. Besides the slate’s visual appeal, its ease of maintenance and cleaning makes it a favorite in the building sector.
   The physical properties of the slates (preferential cleavage, medium hardness, low porosity, high mechanical resistance and good weatherability) allow its wide use as covering in internal and external environments.
   According to North American specifications, based on the ASTM C406 for slate tiles, the graying varieties of the province’s slate are Class 1 with relationship to the water absorption and resistance to acid attacks, suggesting 75-year durability or more in exterior use.
   The market demands well-shaped, squared and calibrated products in accurate dimensions. The recent increase of Brazilian exports, especially of tiles for flooring, billiards, polished slabs and roofing slates, shows the continuing technological development and professional maturity of the Minas Gerais companies.
   Available technological data indicate that the slates of the province compete in quality with the best products in the world. Besides the lower costs and large productivity in quarrying, the Brazilian slates also constitute a mineral resource that is practically inexhaustible.
   Slate has a long history, with exploration of the resource reported since the 10th century. And yet today, slate is still a material in modern step with the North American, European and Asian markets.
   Cid Chiodi is a Brazilian geologist and consultant, and is considered one of the most-knowledgeable sources on the Brazilian stone industry.

This article first appeared in the November 2005 print edition of Stone Business. ©2005 Western Business Media Inc.