Igneous Granite With Feldspar

The specimen shown here is about two inches five centimeters across.

Igneous granite with feldspar.

Cordierite in a peraluminous granite. Alkali feldspar granite some varieties of which are called red granite is a felsic igneous rock and a type of granite rich in the mineral potassium feldspar k spar. Granite is an intrusive igneous rock which means it was formed in place during the cooling of molten rock generally the slower the molten rock cooled the larger it s mineral crystals with k feldspar megacrysts forming in special circumstances greater than 5cm. Strictly speaking granite is an igneous rock with between 20 and 60 quartz by volume and at least 35 of the total feldspar consisting of alkali feldspar although commonly the term granite is used to refer to a wider range of coarse grained igneous rocks containing quartz and feldspar.

Peppered with minor amounts of black minerals. In plane and cross polarized light cordierite looks much like quartz and feldspar and it can be twinned or untwinned. Besides quartz and feldspar a variety of minor and accessory minerals may occur in granitic rocks as dictated by the bulk composition of the magma including its oxidation state and water content and the pressure and temperature at which igneous crystallization took place table 1. Granite is composed mainly of quartz and feldspar with minor amounts of mica amphiboles and other minerals this mineral composition usually gives granite a red pink gray or white color with dark mineral.

Learn more about the properties and uses of granite in this article. It has three distinguishing characteristics. A crystal of imperial topaz on an albite matrix from a pocket in the katlang pegmatite of pakistan. 1 it tends to look dustier than quartz and feldspar little black specks all over the surface such as can be seen here.

Granites are coarse grained intrusive igneous rocks made of two different kinds of feldspar potassium and sodium rich together with quartz and a small granite looking at granite between crossed polarisers makes it easier to distinguish the individual crystals. It forms from the slow crystallization of magma below earth s surface. Granite coarse or medium grained intrusive igneous rock that is rich in quartz and feldspar. The abundance of k spar gives the rock a predominant pink to reddish hue.

The term granitic means granite like and is. Granite is a light colored igneous rock with grains large enough to be visible with the unaided eye. They are importantly dominant minerals in most igneous rock. Specimen is about 4 5 x 3 5 x 3 5 centimeters.

Pegmatite is an igneous rock composed almost entirely of crystals that are over one centimeter in diameter. Plagioclase feldspar group minerals are the most common rock forming minerals. It is a dense rock with a phaneritic texture.