Wisconsin State Stone
DescriptionGranite 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. Wisconsin’s granite comes in a variety of colors, one of which is described as mahogany or ruby red as seen from a distance. At close range, purple and dark gray flecks are visible.
A State SymbolRed granite’s importance to the geology, history, economy, and architecture of Wisconsin motivated its selection as Wisconsin’s state rock in 1971. The impetus to designate a state rock came from the Kenosha Gem and Mineral Society, whose wish was to foster greater awareness of geography among the state’s citizens.
Granite was produced in Wisconsin beginning in the 1850s in Amberg, Berlin, Montello, Utley, Marquette, Redgranite, Waupaca, and Wausau Counties. The red granite was first quarried in the 1890s by William Bannerman, a Scottish immigrant. The town of Redgranite sprang up around one of his quarries.
The main use of the red granite was as paving blocks for large cities such as Chicago and Milwaukee, where the then-prevalent brick or cedar paving blocks could not stand up to the amount of traffic. The granite was quarried in winter and carried 11 miles by horse-drawn sleighs to the railroad stockyard in the town of Berlin pending sale. This arrangement worked out well for the farmers, giving them work between growing seasons.
FormationGranite 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.
Geographic DistributionWisconsin’s granite, widespread in the state, belongs to the Canadian Shield (also known as the Laurentian Plateau), the ancient nucleus of the North American continent. More than half a billion years old, this great body of crystalline Precambrian rock underlies all of Quebec, large extents of other Canadian territories, and part of Wisconsin. Much of the shield is now exposed.
UsesGranite is one of the most favored stones for building construction because of its load-bearing capacity and resistance to weathering. It is also favored for other applications where toughness is essential, such as for breakwaters and riprap (shoreline protection). Granite aggregate is used for railroad ballast and as chip seal for road surfaces.
ProductionTwo quarries in Marathon County continue to produce granite for dimension stone; production in 2005 was 2,550 tons with a value of $1.7 million. Five Wisconsin quarries produced 2.6 million tons of granite aggregate worth $15 million.
Famous ExamplesWisconsin red granite can be seen in many of the state’s buildings and monuments and has also been used for special applications elsewhere. The tomb of Ulysses S. Grant, in New York City, is made of Wisconsin red granite.
Red Granite Falls, actually a series of rapids, is an excellent place to see Wisconsin’s red granite in its natural environment. Probably the most famous granite outcrops in the nation are the towering formations of Yosemite National Park.
Hyderabad, India, and Aberdeen, Scotland, are two cities that are famous for using great quantities of locally quarried granite in their buildings. Aberdeen is nicknamed "the Granite City."
Polished Red Granite
Ornamental Red Granite
Grant's Tomb, in New York City, Is Made of Wisconsin Red Granite
Chemical Formula: SiO2
Color: White, gray, pink or red
|Author: World Trade Press|