Here's why:

* Granite is an igneous rock formed from the slow cooling and crystallization of magma deep within the Earth.

* Magma rises towards the surface, and when it cools and solidifies within the crust, it forms granite.

* Granite is a major component of continental crust. It's often found in mountain ranges and exposed in areas where the crust has been uplifted or eroded.

While it's true that magma originates in the Earth's mantle, granite itself is a product of the cooling process that happens within the crust.