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Posted on April 1, 2006 by Joanne Dorin | Posted under Home Improvement
Granite Counter Top
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Protuberancies of granite tend to form rounded mountain ranges. They also form large hills called tors and terrains of rounded boulders jutting out of flat and sandy soil. Granite will also sometimes occur in a circular depression that is surrounded by a range of hills. These formations are formed by a series of contact metamorphic rocks that have been baked by the heat of intrusive granitic masses. In geology an intrusion is usually a body of an igneous rock that has crystallized from a molten magma below the surface of the Earth. Bodies of magma that solidify underground before they reach the surface of the earth are called plutons, named for Pluto, the Roman god of the underworld. Correspondingly, rocks of this kind are also referred to as igneous plutonic rocks. Granite is not a substance that can be whipped up in a modern day laboratory. There are a lot of enviromental factors that make the granite used in granite counter tops. Granite is nearly always big, hard and tough. Because granite is so tough, it has gained widespread use as a contstruction stone. Granite counter tops are dense. They have an average denisity of 2.75 g/cm3; with a range of 1.74 to 2.80. The etymology of the word granite is Latin. Granite primarily consists of orthoclase and plagioclase feldspars. It also contains quartz, hornblende and biotite. Muscovite and minor accessory minerals such as magnetite, garnet, zircon and apatite are also present in granite. Rarely, a pyroxene is present. Granite has a beautiful coarse grain from the presence of all of these minerals that make is very lovely for a granite counter top. Granite is classified as a coarse grained plutonic rock. Geologists use a QAPF diagram to classify granite. A QAPF diagram is a double triangle diagram which is used to classify igneous rocks based on their mineralogic composition. The acronym, QAPF, stands for "Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)". These are the mineral groups used for classification in QAPF diagram. Granite is classified according to the QAPF diagram for coarse grained plutonic rocks (granitoids) and is named according to the percentage of Quartz, Alkali feldspar (orthoclase) and Plagioclase Feldspar on the A-Q-P half of the diagram. Highly peralkaline forms of granite which are silica undersaturated may have a feldspathoid such as nepheline, and are classified on the A-F-P half of the diagram. Granite is currently known only on Earth where it forms a major part of continental crust. It occurs as a relatively small stock-like mass and as large batholiths often associated with mountain ranges. Although they may appear uniform, batholiths are in fact structures with complex compositions. Batholiths are composed of multiple masses of magma that traveled toward the surface from a zone of partial melting at the very base of the Earth's crust. Small dikes of granitic composition called aplites are associated with granite margins. In some locations very coarse-grained pegmatite masses occur with granite. A dike is an intrusion into a cross-cutting fissure. This means that a dike cuts across other pre-existing layers of rock. A dike is always younger than the rocks that contain it. Dikes are usually in a high angle to near vertical in orientation. Subsequent tectonic deformation can rotate the sequence of strata through which the dike lies so that the it later becomes horizontal. Near horizontal intrusions along bedding planes between strata are called intrusive sills. Granite has been intruded into the crust, outer layer, of the Earth during all of its geologic periods. Granite is widely distributed throughout the continental crust of the Earth and is the most abundant basement rock that underlies the sedimentary covering of the continents. Granite is ancient and aesthetically pleasing when used as a granite counter top. Granite is an igneous rock. Igneous rocks are formed when molten rock cools and solidifies. This can happen with or without crystallization. This can also happen either below the surface as intrusive rocks or on the surface as extrusive rocks. This magma can be derived from either the Earth's mantle or pre-existing rocks made molten by extreme temperature and pressure changes. Granite magma has many potential origins but it must intrude other rocks. Most granite intrusions are at depths within the Earth's crust that is usually greater than 1.5 kilometers and can be up to 50 kilometers deep within the thick continental crust. No one can agree on the origins of granite and this disagreement has led to lots of ways to classify it. The ways to classify granite are basically regional. There is a French way, a British way and even an American way. Generally, the classification knows as the "alphabet soup" classification is used because it classifies granite based on the origin of the melt. These classifications are used by geologist and not usually used by consumers shopping for granite counter tops. Granite is not only used for granite counter tops. It was also used in Antiquity for projects as large and well known as the historic Red Pyramid in Ancient Egypt. The Red Pyramid was named for the color of its exposed granite surfaces. Another pyramid in Egypt, the Menkaure's Pyramid, was constructed using granite blocks and limestone blocks. The historical significance of using granite in modern structures is not always readily apparent. Granite has just proven itself over time to be a sound material. Using granite for granite counter tops is a wise choice. About The Author: Joanne is an author of Decorz.com. If you're looking for more countertops & decorating ideas for your home and garden visit http://www.decorz.com. |
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