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Quarry to Kitchen Granite results from the melting of rock 16 to 25 miles (26 to 40 kilometers) underground. As rock's temperature reaches 1200 degrees Fahrenheit (650 degrees Centigrade), the minerals that form granite begin to melt. Lighter than the surrounding solid rock, this liquid magma rises, cools, and crystallizes beneath Earth's surface. Although granite comes from many kinds of rocks, it comes in relatively few colors: white, pink, gray, red, or brown, and rarer greens and blues (which are among Brazilian specialties). Stone's Strengths — And Vulnerabilities While clients may admire the visible mosaic of individual crystals in granite, architects appreciate that this hard and durable material is also the strongest building stone. Nevertheless, alkaline chemicals can cause granite to break down, and oxidation alters its color. In an effort to help architects, designers, and builders choose appropriate stones for different projects, the Brazilian Association for Dimension Stones Industry provides a catalog and technical specifications for many Brazilian marbles and granites. Examples include the white marble Branco Paraná, the multicolored granite Amêndoa Chocolate, the pink granite Bege Dunas, and the green granite Verde Tunas, all from the Brazilian state of Paraná. Throughout human history, people have chosen marble for many reasons: rulers, for its strength; archivists and treasurers, for its resistance to fire and erosion; and priests, for its beauty. However, acidic environments, pollution, and abrasion cause marble to deteriorate. Furthermore, if exposed to the weather, marble can freeze, rupture, and detach from buildings. Nonetheless, designers and clients continue to revere the unique veins, the translucence, and rare fragments of fossils found in various marbles. A group of small marble and granite companies in Paraná have found a way to compete with big firms for large export contracts. They formed a "Local Productive Arrangement," or LPA, named Brazilian Marble and Granite (BMG), in which the 15 member companies pool their respective specialties to produce reasonably priced finished items. From Earth to Countertop Paraná has both marble and granite quarries. Due to its origin, granite usually lies deeper than marble. Current extraction procedures involve quarry workers using drills, steel feathers and wedges, and diamond-wire saws (on marble), and, perhaps, explosives, or jet-burner lances (on granite) to separate walls of stone from the quarry face, then to subdivide these large pieces into rough blocks that often vary in size from 175 to 350 cubic feet (5 to 10 cubic meters). From the quarries, trucks transport stone blocks to fabrication shops, where gang saws, wire saws, or rotating diamond saws slowly cut them into slabs. The parallel blades of a gang saw may take a week to slice through one granite block. These slabs might be 6.5 feet (2 meters) high and 13 feet (4 meters) long, with thickness determined by the type of stone and its unique technical specifications. Next, shop technicians trim the rough slabs — and sometimes patch and polish them — in preparation for export. Eventually, slabs will be edged, planed, and given a specified surface finish. Additional options include planing the slabs to a certain molding profile, turning them on a lathe, and custom carving. Production, transportation, and sales structures affect international supplier markets in decorative stone, which has resulted in Italy, China, and Japan variously cooperating and competing with Brazil as their industries have developed. For instance, in the past Japanese companies would purchase rough blocks of Brazilian stone, ship them to China for cutting and finishing with cheap labor, then import finished products to Japan for use in construction. More recently, Chinese companies began to import blocks and rough slabs of Brazilian stone directly, then would manufacture finished products and export them cheaply to countries like the United States. >>> Discuss this article in the Architecture Forum...
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