Pink banded gneiss. Gneiss is a common metamorphic rock. Under high temperature and pressure conditions, the minerals in gneiss...Read More >>Pink banded gneiss. Gneiss is a common metamorphic rock. Under high temperature and pressure conditions, the minerals in gneiss form bands of mafic (rich in magnesium and iron) minerals and felsic (rich in silicon, oxygen, aluminium, sodium and potassium) minerals. Metamorphic rocks are formed when rocks are subjected to such great pressure and heat that their mineral composition is altered. The original rocks may be sedimentary, igneous or metamorphic rocks. Marble, slate, gneiss and quartzite are all examples of metamorphic rocks. Some minerals in rocks undergoing metamorphism may be transformed into gemstones.
Where two pieces of continent are forced together by the movement of tectonic plates, the land can be pushed up to great heights. The rocks are squeezed so tightly that they begin to change. The chemicals inside the rocks re-arrange themselves into new minerals.
Marble is metamorphosed limestone. The typical swirling veins come from the various mineral impurities in the limestone, such as clay, silt, sand or iron oxides.
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