Not to be snooty but diorite and granite are very different. Their formation is similar as far as where they come from and method but while granite is quartz, feldspar and mica diorite is mostly dark plagioclase feldspar with very little quartz or mica. Once the quartz and mica increases it's really a different rock.Also diorite can vary quite a bit. Diorite is a very hard rock and is difficult to work with.

I'll bet you didn't know the code of Hammurabi was carved on diorite.