Metamorphic: Tough rock with layers (foliation) of light and dark minerals, often curved; various colors; often glittery from mica....Metamorphic rocks are the third great class of rocks. These are what happens when sedimentary and igneous rocks become changed, or metamorphosed, by conditions underground. The four main agents that metamorphose rocks are heat, pressure, fluids and strain. These agents can act and interact in an infinite variety of ways. As a result, most of the thousands of rare minerals known to science occur in metamorphic ("shape-changed") rocks. Metamorphism acts at two scales, the regional scale and the local scale. This looks like your "rock" cheers, Mike