Thin Section Description Of Granite

Biotite metaluminous granite showing a close up of one crystal.

Thin section description of granite.

Granites can be predominantly white pink or gray in color depending on their mineralogy the word granite comes from the latin granum a grain in reference to the coarse grained structure of such a completely crystalline rock. Granite ˈ ɡ r æ n ɪ t is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Petrography is a branch of petrology that focuses on detailed descriptions of rocks someone who studies petrography is called a petrographer the mineral content and the textural relationships within the rock are described in detail. This sample is a less evolved portion of the intrusion which was associated with the tourmaline and topaz rich intrusions and mineralisation.

Quartz thin section photomicrographs are taken in plane polarized light and cross polarized light and can easily be recognized under the microscope. This means that biotite in standard thin sections rarely goes completely extinct. The classification of rocks is based on the information acquired during the petrographic analysis petrographic descriptions start with the field notes at the. Biotite brown grains in plain light and pinkish brown with crossed polars the brown color is due to a property called.

By comparing the plane polarized light left and crossed polarizer right images we can see that there are three minerals in this granite. Strictly speaking granite is an. Fluorapatite ilmenite and titanite are also present in minor amounts. This sample of biotite rich granite comes from the luxulyan quarry in the luxulyan valley in south east cornwall.

The second is a thin section rock description where you have a slice of the rock which is on a glass slide making it possible to view the rock under a microscope. Damage produced during thin section grinding causes speckles of light in the biotite where the crystal lattice has been deformed. To link to this object paste this link in email im or document to embed this object paste this html in website. The large pink carlsbad twinned k feldspar megacrysts dominate the thin section.

Hand specimen descriptions focus on physical properties of the rocks whereas the thin section descriptions looks at optical properties instead.