Igneous rocks that cool and harden under the surface of the crust are called intrusive igneous rocks.

Here's why:

* Intrusive means that the molten rock (magma) intrudes into existing rock layers.

* Since they cool slowly beneath the surface, they have larger crystals and a more coarse-grained texture.

Some examples of intrusive igneous rocks include:

* Granite: A common, light-colored rock with large crystals.

* Gabbro: A dark-colored rock with large crystals.

* Diorite: A medium-colored rock with large crystals.

* Peridotite: A dark-colored rock with large crystals, often found in the Earth's mantle.

Let me know if you have any other questions about igneous rocks!