Metamorphic rocks arise from the transformation of existing rock types in a process called metamorphism which means change in form. The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 ?C) and pressure (1500 bars) causing profound physical and/or chemical change. The protolith may be a sedimentary rock an igneous rock or another older metamorphic rock. Metamorphic rocks make up a large part of the Earth's crust and are classified by texture and by chemical and mineral assemblage (metamorphic facies). Contains 6 types of Metamorphic rocks: 1 each of Quartzite Slate Marble Gneiss Anthracite and Schist Great set to learn about rock identification. Intended to be parts for use with science projects science fairs etc. and are provided with minimal to no operating instructions.
