Composition Of Granite Gneiss

Gneiss is a high grade metamorphic rock having many of the aerial photograph characteristics of granite.

Composition of granite gneiss.

There are three major types of rocks as sedimentary rocks igneous rocks and metamorphic rocks. Gneiss is a hard rock that has a mineral composition similar to granite as it contains the feldspar mica and quartz. The main difference between gneiss and granite is that gneiss is a type of metamorphic rock whereas granite is a type of igneous rock. Composition and texture of gneiss although gneiss is not defined by its composition most specimens have bands of feldspar and quartz grains in an interlocking texture.

They are largely recrystallized but do no longer deliver large quantities of micas chlorite or different platy minerals. It was originally a mining term meaning a country rock in the ore mountains erzgebirge which contained metalliferous veins. Paragneiss is gneiss derived from sedimentary rock such as sandstone. Chemical composition of gneiss gneissic rocks are usually medium to coarse foliated.

This is a rock that is formed from pre existing igneous rocks such as granite that have been subject to conditions of high pressure and temperature. This specimen has a composition of an ordinary granite. Gneiss is made up of coarse grained minerals such as quartz and feldspar. Granite gneiss definition is a rock consisting of an orthogneiss or paragneiss having the composition of a granite.

The term gneiss was brought to scientific usage from the german language. Ortho gneiss is essentially metamorphosed granite so it too is similar in appearance to granite. Gneisses which can be metamorphosed igneous rocks or their equivalent are termed granite gneisses diorite gneisses and so on. For the casual student it is convenient to think of a gneiss as a rock with parallel somewhat irregular.

Gneiss metamorphic rock that has a distinct banding which is apparent in hand specimen or on a microscopic scale. Orthogneiss is gneiss derived from igneous rock such as granite. Gneiss usually is distinguished from schist by its foliation and schistosity. Schist is a metamorphic rock usually formed originally from shale.

Pink k feldspar gray quartz and black biotite. Granitic gneiss has a mineral composition similar to that of granite. These bands are usually light in color and alternate with bands of darker colored minerals with platy or elongate habits. Rocks are naturally occurring solid masses or aggregates of minerals.

Gneiss is formed by high temperature and high pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss displays a well developed foliation and a poorly developed schistosity and cleavage. Width of sample 11 cm.