Syenites are coarse-grained intrusive rocks that are relatively rare on Earth. The best-known occurrences of them can be found in the United States and Germany, where they are sometimes quarried for use as building stones. As noted by Pliny the Elder, the texture of syenites is the same as that of granites, the primary difference between the two being only the amount of quartz they contain. Syenites are often differentiated from one another based upon their constituent ferromagnesian mineral. Some of the most common types of the rock observed are hornblende syenite, augite syenite, and mica syenite.