Thin Section Description Of Granite

The mineralogy of this granite is relatively simple biotite quartz and two feldspars plagioclase and k feldspar.

Thin section description of granite.

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. Granite ˈ ɡ r æ n ɪ t is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Hand specimen descriptions focus on physical properties of the rocks whereas the thin section descriptions looks at optical properties instead. The classification of rocks is based on the information acquired during the petrographic analysis petrographic descriptions start with the field notes at the.

Damage produced during thin section grinding causes speckles of light in the biotite where the crystal lattice has been deformed. Biotite metaluminous granite showing a close up of one crystal. This means that biotite in standard thin sections rarely goes completely extinct. Quartz thin section photomicrographs are taken in plane polarized light and cross polarized light and can easily be recognized under the microscope.

This sample is a less evolved portion of the intrusion which was associated with the tourmaline and topaz rich intrusions and mineralisation. This sample of biotite rich granite comes from the luxulyan quarry in the luxulyan valley in south east cornwall. The large pink carlsbad twinned k feldspar megacrysts dominate the thin section. These are photographs of a thin section of granite magnification 10x perhaps the most common igneous rock we encounter.

The thin section illustrates the quartz rich nature of the rock which. Strictly speaking granite is an. By comparing the plane polarized light left and crossed polarizer right images we can see that there are three minerals in this granite. Biotite brown grains in plain light and pinkish brown with crossed polars the brown color is due to a property called.

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.