Linked from
The 6 pages that link to Diorite, each with the reason it gives.
GraniteCompared with: Its lower silica content and darker appearance distinguish it from granite.
GabbroCompared with: Diorite is generally more silica-rich and less mafic than gabbro.
TonaliteCompared with: Diorite resembles tonalite in feldspar makeup but contains much less quartz.
GranodioriteCompared with: Its lower quartz content distinguishes it from quartz-rich granodiorite.