Thin Section Description Of Granite

These are photographs of a thin section of granite magnification 10x perhaps the most common igneous rock we encounter.

Thin section description of granite.

The mineralogy of this granite is relatively simple biotite quartz and two feldspars plagioclase and k feldspar. Fluorapatite ilmenite and titanite are also present in minor amounts. Quartz thin section photomicrographs are taken in plane polarized light and cross polarized light and can easily be recognized under the microscope. Biotite metaluminous granite showing a close up of one crystal.

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. 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 means that biotite in standard thin sections rarely goes completely extinct. Biotite brown grains in plain light and pinkish brown with crossed polars the brown color is due to a property called.

To link to this object paste this link in email im or document to embed this object paste this html in website. This sample of biotite rich granite comes from the luxulyan quarry in the luxulyan valley in south east cornwall. This sample is a less evolved portion of the intrusion which was associated with the tourmaline and topaz rich intrusions and mineralisation. Hand specimen descriptions focus on physical properties of the rocks whereas the thin section descriptions looks at optical properties instead.

By comparing the plane polarized light left and crossed polarizer right images we can see that there are three minerals in this granite. The classification of rocks is based on the information acquired during the petrographic analysis petrographic descriptions start with the field notes at the. Strictly speaking granite is an. 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.

The thin section illustrates the quartz rich nature of the rock which.