More specifically, they are intrusive igneous rocks, meaning they solidified from magma beneath the Earth's surface.

Here's a breakdown:

* Igneous Rocks: Formed from the cooling and solidification of molten rock (magma or lava).

* Intrusive Rocks: Form when magma cools and solidifies slowly within the Earth's crust.

* Extrusive Rocks: Form when lava erupts onto the Earth's surface and cools quickly.

Dolerite is closely related to basalt, which is an extrusive rock. The difference lies in their cooling rate and resulting mineral grain size. Dolerite has larger crystals than basalt due to its slower cooling.