Syenite is a type of intrusive igneous rock that is similar in appearance and composition as granite. In fact, the term was coined by Pliny the Elder to refer to a type of hornblende granite similar to that found in Syene, Egypt.

View a second image of Hedenbergite Syenite

Relatively rare, syenites are much less common than granites, diorites, and many other rocks. The coarse-grained specimens are most heavily located in a few regions of Germany and the United States, though they appear in some other locales as well. Despite their comparative rarity, the hard rocks are sometimes quarried for use as building stones and are typically utilized for the same type of applications as the granites.

Although syenite is similar to granite in many regards, the rock contains little or no quartz. Indeed, essentially syenite is comprised of a ferromagnesian mineral and an alkali feldspar, although some varieties also contain a feldspathoid mineral. The exact type of these basic components may vary significantly, and many syenites are named or classified by the dominant mineral they contain. Hedenbergite syenite, for instance, is a type of syenite that contains significant amounts of hedenbergite, a member of the pyroxene family of minerals. Hedenbergite, which is usually dark green or black in color, is a calcium magnesium silicate that is closely related to diopside.