Granite and Marble
- PDF / 5,231,677 Bytes
- 4 Pages / 576 x 777.6 pts Page_size
- 92 Downloads / 240 Views
Granite and Marble Two types of stone, granite and marble, have been used since ancient times for building, decoration, and sculpture. Granite is used particularly in applications that require great resistance to weathering, such as in monuments, tombstones, road curbings, building facings, and foundations. Granite is the most common igneous rock (formed from solidified magma), and is found in masses that may extend for tens or hundreds of miles. Granite varies in color and is usually light, with gray predominating, but is also found in pink, yellow, red, and green. The coloration is determined by impurities in granite's most dominant mineral constituents, feldspar and quartz. Other components of granite include muscovite, biotite, pyroxene, and hornblende. In addition to its pleasing colors, granite has several other advantages: it possesses great strength and durability, has a homogeneous texture, and is not too difficult to work with. Granite is the hardest of all building stones. Disadvantages include its rough surface (which takes on a dirty appearance) and its tendency to spall, or crumble, when directly exposed to fire. Prior to World War II, the widespread use of macadam and concrete for roads, along with the occurrence of the Great Depression of the 1930s (which brought construction to a virtual standstill), caused a downturn in granite production that lasted until the post-war building boom. Marble, a metamorphic rock usually derived from limestone (in which the calcite has been recrystallized), is a favorite stone of architects because of its beauty and the ease with which it can be worked, as well as the warmth of its polished surfaces. The calcite grains in marble reflect light penetrating through minute cracks in the surface, producing a luminescence. Marble's resistance to abrasion makes it popular for stair treads and flooring. The hardness of marble is 3 on the Mohs scale. Marble has been used in constructing such famous landmarks as the Parthenon in Athens, the Taj Mahal in India, the Lincoln Memorial in Washington D.C., and St. Peter's Basilica in Rome. Because granite and marble have been extensively used since ancient times, quarrying of the stone was a major industrial activity. Beginning in ancient Egypt, granite or marble quarries were
the sites for large construction projects. From these sites, the Egyptians could move blocks weighing up to a million kilograms, hauling them to distant building sites. Most of these quarries were open-faced, though workers could extend tunnels several hundred meters into cliffs to reach inclusions of highquality granite or marble. After stripping away the top layers of dirt and weathered stone, rows of holes were drilled into the exposed rock with metal bow drills. Wooden wedges were driven tightly into the holes, then doused with water; the wood absorbed the water, which expanded the wedges enough to crack the rock along the line of holes. Since granite is much harder than marble, workers used not only picks but also pounding balls of dolerite (a very hard,
Data Loading...
