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Two Half Crystals With Different Brightness

Edit:Xiamen Youstar Imp & Exp Co.,LtdUpDate:Jun 07, 2018

Granite is an intrusive rock in the acidic (SiO2>66%) magmatic rocks, which is the most common type of rock in this type, mostly light red, light gray, gray and so on. Medium coarse grain, fine grain structure, massive structure. There are also some miscellaneous structures, globular structures, and quasi-like structures. The main minerals are quartz, potash feldspar and acid plagioclase, and the minor minerals are biotite, amphibole, and sometimes a small amount of pyroxene. There are many types of accessory minerals, magnetite, vermiculite, zircon, apatite, tourmaline, and fluorite. Quartz is the most abundant of all kinds of magmatic rocks, its content can be from 20-50%, a few up to 50-60%. The content of potassium feldspar is generally more than that of plagioclase, and the proportion of the two is usually two-thirds of the total length of feldspar. The plagioclase accounts for one-third of the total amount of feldspar, and the potassium feldspar is more in granite. It is pale red, grey and grey. The gray-white potassium feldspar and plagioclase are often not easily distinguished on hand specimens. At this time, we must carefully observe the double crystal characteristics of these two types of feldspar, because the plagioclase has polycrystalline double crystals, and when the hand specimens are rotated, there are regular light-dark and white polygraphs on the plagioclase crystals, and the potassium feldspar For the cassette double crystals, two halves of crystals with different brightness levels appear.

Granite can also be further named according to the type of dark-colored minerals, such as dark-colored minerals are mainly biotite, which can be called biotite granite, which is a common type of granite. Such as biotite and muscovite, their content is nearly equal, can be called two mica granite, if dark-colored minerals are mainly hornblende, it is called hornblende granite, if the dark-color mineral is mainly pyroxene, it is called Stone granite, which contains almost no dark minerals, is called white rock.