The specific mineral in granitic magma that typically crystallizes within the temperature range of approximately 640°C to 930°C is muscovite (a type of mica).
When muscovite and other minerals in granitic magma crystallize completely, the resulting rock often exists within the upper- to mid-greenschist facies of metamorphism, particularly under conditions of moderate temperature and pressure.
Note that the actual facies may depend on the specific pressure conditions and the presence of other metamorphic minerals in the rock.