Alkalic, or alkali, syenites are a special group of rocks that are differentiated from other syenites by the fact that they contain a feldspathoid mineral, such as sodalite, leucite, or nepheline. They also contain significantly less quartz than other syenites. Relatively rare on a global scale, one of the best examples of an alkalic syenite can be found at Mont St. Hilaire in Quebec, Canada. The most studied alkalic syenite is nephelinesyenite, which is remarkable for its extensive variation in mineralogy, habit, and appearance. This unusual rock is occasionally utilized in the production of glass and ceramics.