Here's why:

* Metamorphic rocks are formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are changed by heat, pressure, or chemical reactions.

* Unakite is specifically a metamorphic rock formed from the alteration of granite. The green epidote and pink orthoclase feldspar that give it its distinctive color are the result of this metamorphic process.

Let me know if you have any more questions about rocks!