Information AboutGranite |
| CATEGORIES ABOUT GRANITE | |
| igneous rocks | |
| granite domes | |
| stone | |
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, valley of the Merced River ]] . The quarrying consists of splitting up the blocks]] Granite (, Felsic , Igneous Rock . Granites are usually medium to coarsely crystalline, occasionally with some individual crystals larger than the groundmass forming a rock known as Porphyry . Granites can be pink to dark gray or even black, depending on their chemistry and mineralogy. 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 nearly always massive, hard and tough, and it is for this reason it has gained widespread use as a construction stone. The average Density of granite is 2.75 g·cm−3 with a range of 1.74 g·cm−3 to 2.80 g·cm−3. The word granite comes from the Latin ''granum'', a grain, in reference to the coarse-grained structure of such a Crystal line rock. MINERALOGY 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 , Sanidine , or Microcline ) and Plagioclase feldspar on the A-Q-P half of the diagram. Granite-like rocks which are Silica-undersaturated may have a Feldspathoid such as Nepheline , and are classified on the A-F-P half of the diagram (Figure 1). True granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase the rock is referred to as alkali granite. When a granitoid contains <10% orthoclase it is called Tonalite ; pyroxene and amphibole are common in tonalite. A granite containing both muscovite and biotite Mica s is called a binary or ''two-mica'' granite. Two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. The Volcanic equivalent of Plutonic granite is Rhyolite . Chemical composition |
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