New Hampshire State Stone
Granite is a hard, crystalline, plutonic igneous or metamorphic rock. It varies in composition depending on the parent rock that melts or partially melts to form it; the dominant components are quartz and feldspar, which form the lighter-colored parts of the rock. The darker parts may be biotite, hornblende, muscovite, pyroxene, or other minerals.
Granite’s medium-to-large crystal size gives it a granular appearance, thus its name, from the Latin granum. Granite is most often predominantly white, gray, pink, or red. Green and brown granites also occur.
A STATE SYMBOL
New Hampshire is a rocky state. Quartz, quartzite, schist, and slate are among the abundant types of bedrock other than granite. The choice of granite as the official state rock in 1985 has as much to do with the figurative meaning of granite as with its prevalence in the state. New Hampshire has long been known as "the Granite State" because of its people’s reputation for toughness and endurance.
Granite has been quarried in the state since the 1700s and is in evidence in the state’s architecture as well as its natural scenery. A former emblem of the state, the "Old Man of the Mountain" was a craggy granite outcrop resembling the profile of a face. Although this famous natural structure collapsed in 2003, it is represented on the New Hampshire commemorative quarter.
Granite is plutonic, meaning that it forms underground, and is at least sometimes igneous, or formed from magma. The underground origin allows slow cooling of the magma or parent rock and accounts for the medium to large crystal size characteristic of the rock.
Geologists have searched for means to explain how so much granite rises from the earth’s lower crust where it originates into the upper crust. Tectonic uplift and surface erosion may lead to granite’s exposure at the surface; however, these forces are not sufficient to account for the emplacement of most granite. Major theories presume that granite moves upward through surface rocks while it is still relatively hot, either pushing the other rocks aside or filling gaps at fault lines.
Another disputed question is whether the majority of granite is actually metamorphic (silicified from softer rock). The prevailing theory remains that granite is primarily igneous.
Granite is widespread in continental landforms. It is the primary material of numerous mountain ranges formed above tectonic subduction zones; low-relief granite plutons, such as the vast Laurentian Shield, underlie flatter topography as well. By contrast, the ocean floor is primarily made of basalt.
USES OF GRANITE
Granite is one of the most favored stones for building construction because of its load-bearing capacity and resistance to weathering. It is also a material of choice for other applications where toughness is essential, such as for breakwaters and riprap (shoreline protection), and for interiors where its hardness and glossy finish are both practical and beautiful. Granite aggregate is used for railroad ballast and as chip seal for road surfaces.
In spite of its small size, New Hampshire ranks fourth nationally in granite production. In 2006, nine quarries in New Hampshire produced 2.6 million tons of granite aggregate worth a total of $23.3 million (data on dimension granite have been withheld by the quarries). The largest quarry of granite for dimension stone is located outside the capital city, Concord, and quarries 25,000 tons annually, cutting a large amount of its product for curbstones. Nationwide, 30 companies quarry granite in 17 states, producing 416,000 tons with a total value of $106 million.
Granite is used throughout the world in buildings and monuments. Thirty thousand tons of granite from New Hampshire were used to build the Library of Congress in Washington, DC. Aberdeen, Scotland, and Hyderabad, India, are two cities that have used great quantities of locally quarried granite in their buildings; Aberdeen is nicknamed "the Granite City." Impressive natural features made of granite include the towering formations of Yosemite National Park in California.
Chemical Formula: SiO2
Color: White, gray, pink or red
|Author: World Trade Press|