1)Both igneous rocks and sedimentary rocks may be subjected to high temperature and pressure which )causes metamorphism which changes the structure and texture of rocks.
2)Metamorphic rocks show foliated structure. The thickness of this foliation may vary from a few centimeters to many metres. If the thickness of this foliation is less, then individual aggregate may exhibit foliation which is not a desirable characteristic in aggregate.
2)However, many metamorphic rocks particularly quartzite and gneiss have been used for production of good concrete aggregates.
