jancancook
Posts : 159 Join date : 2011-02-23
| Subject: Granite Wed Mar 16, 2011 9:39 pm | |
| Granite (pronounced /ˈɡrænɨt/) is a common and widely occurring type of intrusive, felsic, igneous rock. Granites usually have a medium- to coarse-grained texture. Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is sometimes known as a porphyry. Granites can be pink to gray in color, depending on their chemistry and mineralogy. By definition, granite has a color index (the percentage of the rock made up of dark minerals) of less than 25%. Outcrops of granite tend to form tors and rounded massifs. Granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. Granite is usually found in the continental plates of the Earth's crust. Damp cigaretangina medication | |
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