29. Metamorphic rocks are rocks that have "morphed" into another kind of rock. These rocks were once igneous or sedimentary rocks. How do sedimentary and igneous rocks change? The rocks are under tons and tons of pressure, which fosters heat build up, and this causes them to change. If you exam metamorphic rock samples closely, you'll discover how flattened some of the grains in the rock are.

31. Metamorphic rocks are the type of rock that has changed, or “morphed” into another type of rock. The word metamorphic comes from “meta” which means to change and “morph” which means to form. Metamorphic rocks were created originally as igneous rocks which later transitioned into sedimentary rocks. They changed due to an extremely large amount of pressure. This heavy pressure causes major heat build up, and as we have learned throughout the site, heat causes rocks to change form, whether it be shape, colour or size. It is very easy for any rock to become a metamorphic one, as the only factor that contributes, occurs when minerals change and become unstable and unable to sustain the new environmental conditions. The main changes that can affect the equilibrium and the minerals is rise in temperature and pressure, as previously stated.
Slate- Often used for flooring and counters
Schist
Gneiss-Often used in jewelry
Marble- Often used for flooring, counter tops and sculptures

32.                      
Schist rocks are metamorphic. These rocks can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat and pressure, these rocks were transformed into this new kind of rock.

33.                      
Gneiss rocks are metamorphic. These rocks may have been granite, which is an igneous rock, but heat and pressure changed it. You can see how the mineral grains in the rock were flattened through tremendous heat and pressure and are arranged in alternating patterns.