Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite and diopside, hypersthene, bronzite or enstatite. They are classified (see diagram below) into clinopyroxenites, orthopyroxenites, and the websterites which contain both pyroxenes. Closely allied to this group are the hornblendites, consisting essentially of hornblende and other amphiboles.
They are essentially of igneous origin, though some pyroxenites are included in the metamorphic Lewisian complex of Scotland. The pyroxene-rich rocks which result from the contact metamorphism of impure limestones are described as pyroxene hornfelses (calc-silicate hornfelses).