How did it form? Diorite is a course-grained igneous rock that forms when magma rich in silica cools slowly deep within the Earth's crust.

Where does diorite come from?

Diorite formed deep within the Earth's crust from cooling magma that never made it to the surface. It usually occurs as quite small intrusions often associated with larger intrusions like granite. Slow cooling produces the large crystals.

Is diorite formed from lava?

Partial melting of the oceanic plate produces a basaltic magma that rises and intrudes the granitic rock of the continental plate. There, the basaltic magma mixes with granitic magmas or melts granitic rock as it ascends through the continental plate. ... Diorite forms if this type of melt crystallizes below the surface.