Composition Of Granite Gneiss

Chemical composition of gneiss gneissic rocks are usually medium to coarse foliated.

Composition of granite gneiss.

This specimen has a composition of an ordinary granite. Granitic gneiss has a mineral composition similar to that of granite. Schist is a metamorphic rock usually formed originally from shale. In fact primary gneiss is largely indistinguishable from granite at aerial photograph scales.

Gneiss usually is distinguished from schist by its foliation and schistosity. These bands are usually light in color and alternate with bands of darker colored minerals with platy or elongate habits. Gneiss displays a well developed foliation and a poorly developed schistosity and cleavage. Gneiss is a hard rock that has a mineral composition similar to granite as it contains the feldspar mica and quartz.

Gneiss metamorphic rock that has a distinct banding which is apparent in hand specimen or on a microscopic scale. Gneiss forms at higher temperatures and pressures than schist. It is a step above gneiss in the metamorphic process meaning schist has been subjected to less intense heat and pressure. Pink k feldspar gray quartz and black biotite.

Gneiss is made up of coarse grained minerals such as quartz and feldspar. They are largely recrystallized but do no longer deliver large quantities of micas chlorite or different platy minerals. Ortho gneiss is essentially metamorphosed granite so it too is similar in appearance to granite. The main difference between gneiss and granite is that gneiss is a type of metamorphic rock whereas granite is a type of igneous rock.

Gneiss is formed by high temperature and high pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. It was originally a mining term meaning a country rock in the ore mountains erzgebirge which contained metalliferous veins. Gneiss is a high grade metamorphic rock having many of the aerial photograph characteristics of granite. Orthogneiss is gneiss derived from igneous rock such as granite.

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. There are three major types of rocks as sedimentary rocks igneous rocks and metamorphic rocks. Rocks are naturally occurring solid masses or aggregates of minerals. Width of sample 11 cm.

For the casual student it is convenient to think of a gneiss as a rock with parallel somewhat irregular. 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.