What is diorite in geology ?

Diorite : definition

Streckeisen diagrams (or QAPF diagrams) - Classification of plutonic and volcanic rocks
A diorite is a grainy magmatic rock with whitish and greenish or blackish crystals, composed of 50 to 75% of plagioclases (oligoclase and especially andesine), amphibole (green hornblende), some biotites and rare augites. It is distinguished from gabbro by the absence of olivine, and from granite by its absence of quartz or in less quantity due to a lower richness in silica.
Quartz diorites (tonalite, trondhjemite), rare rocks, have the particularity of possessing small quantities of quartz and alkaline feldspar, these two cumulative minerals not exceeding 10% of the mass of the rock. Diorites form small isolated massifs or linked to granite massifs.
Its volcanic equivalent is andesite, which is much more important from a quantitative point of view.