23 - Augen Geniss

Hello friends, Welcome to the Rock Repository at the Department of Geology, Shivaji Science College, Nagpur.

"I am Augen Gneiss, a high grade metamorphic rock born from the transformation of granite. Augen, which means 'eyes' in German, is characterized by distinctive elliptic or lenticular shear-bound grains (porphyroclasts) of feldspar, surrounded by finer-grained material. The finer grains gracefully deform around the more resilient feldspar, creating a unique texture. As a gneiss, I proudly exhibit distinct foliation, showcasing alternating layers of diverse minerals. These layers form bands, known as gneissic banding, without a defined cleavage. The darker bands boast a higher concentration of mafic minerals like hornblende and biotite, while the lighter bands showcase more felsic minerals like feldspar or quartz, enriched with lighter elements such as aluminum, sodium, and potassium

Now, let's dive into the diverse classifications of gneiss. There's Orthogneiss, born from the metamorphism of igneous rocks, and Paragneiss, a result of the metamorphism of sedimentary rocks. We gneisses proudly grace the ancient crusts of continental shields or cratons, often serving as the steadfast older basement rocks beneath various formations." Thank you for visiting.