The preexisting rocks may be igneous sedimentary or other metamorphic rocks.
A metamorphic rock formed from granite.
The view shown in the photo is about 12 inches across.
Granite is an igneous rock that forms when magma cools relatively slowly underground.
It is formed by dynamic metamorphism at high temperatures and high pressures that aligns the grains of mica hornblende and other flat or elongated minerals into thin layers or foliation.
Foliated means the parallel arrangement of certain mineral grains that gives the rock a striped appearance foliation forms when pressure squeezes the flat or elongate minerals within a rock so they become aligned.
It is usually composed primarily of the minerals quartz feldspar and mica.
Gneissgranite gneiss is a metamorphic rock formed from granite gneiss schist quartzite.
Granite gneiss can also form through the metamorphism of sedimentary rocks.
Gneiss ˈnaɪs is a common and widely distributed type of metamorphic rock.
Slate is another common metamorphic rock that forms from shale.
Metamorphic rock any rock that results from the alteration of preexisting rocks in response to changing conditions such as variations in temperature pressure and mechanical stress and the addition or subtraction of chemical components.
These rocks develop a platy or sheet like structure that reflects the direction that pressure was applied.
Orthogneiss is gneiss derived from igneous rock such as granite.
The original rock is subjected to heat temperatures greater than 150 to 200 c and pressure 100 megapascals 1 000 bar or more causing profound physical or chemical change the protolith may be a sedimentary igneous or existing metamorphic rock.
Gneiss is formed by high temperature and high pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks.
Some kinds of metamorphic rocks granite gneiss and biotite schist are two examples are strongly banded or foliated.
A photograph of polished gneiss from the stock of a countertop vendor.
Schist comes from the ancient greek for split through latin and french.
Metamorphic rocks arise from the transformation of existing rock types in a process called metamorphism which means change in form.
The end product of their metamorphism is a banded rock with a mineralogical composition like granite.
What rock does granite form from heat and pressure.
Schist is a metamorphic rock that comes in almost infinite variety but its main characteristic is hinted at in its name.
In migmatite you can see metamorphic rock that has reached the limits of metamorphism and begun transitioning into the igneous stage of the rock cycle by melting to form magma.
The granitic rock in migmatite probably originated from partial melting of some of the metamorphic rock though in some migmatites the granite may have intruded the rock from deeper in the crust.
