Syenite is an intermediate plutonic rock. The bulk rock K2O + N2O content generally reaches 9%, and the chemical composition is consistent with that of alkali rocks. Syenite contains no quartz or only a small amount (<5%), and the remainder is mainly alkali feldspar. Its nonmenclature, such as hornblende syenite, biotite syenite and pyroxene syenite, is based on the amount of dark minerals contained in the rock. For example, the rock at Nankou in Beijing is hornblende syenite, and the rock at Linxian in Shanxi Province is tveitasite.