Granite with mineral composition of feldspar and quartz is a hard igneous rock. Its structure is also different like crystalline. Geologists say that granite comes in many colours. Again, the colour of the rock is largely depends upon the composition of the minerals which basically gives colour to all granite rocks from pink to grey. If you look at the different colours of granite then you can definitely determine the actual mineral content or composition of that particular rock. Igneous rock which is one fifth quartz is also granite. The mineral formation of granite and gneiss is quite similar but high pressure and temperature changes basically form granite. Different colours of granite rocks tell you all about the actual mineral composition is different in a variety of rocks. If you find more pink shaded rocks, it is a large possibility that it has extra amount of alkali feldspar. According to geologists, granite has magnetic origins and it is found in the crust of the Earth. Granite is a very hard rock which is used in modern day construction as most people have counter tops or other items that are made of this hard rock somewhere in their home or office.
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Gneiss has mineral composition of mica, feldspar and quartz. The mica is an extra mineral in gneiss and that is why it is different from granite. Gneiss rocks form from pre-existing granite rocks with the pressure and high temperature in the crust of the Earth. The formation of gneiss rocks is done when nomenclature leads to metamorphosis. This process takes many years to complete as it is a natural method to get igneous rocks to form into gneiss. The parent rocks are still granite and some other diorite gneiss, biotite gneiss and garnet gneiss. However, gneiss formed from different hard conditions like high pressure and temperature. The process of formation of igneous rock into gneiss is called metamorphosis. The alternation of granite creates gneiss rocks. Many minerals are in the shape of bands in gneiss as well.
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