An ultrabasic, igneous rock consisting of essential clinopyroxene, orthopyroxene, and olivine. The ferromagnesian minerals are magnesium-rich, the pyroxenes dominating olivine, which is usually less than 40% by volume. Different types of pyroxenites are defined using the ratio of clinopyroxene to orthopyroxene to olivine. These include orthopyroxenite, websterite, clinopyroxenite, and olivine-bearing versions of these. Pyroxenites are found as cumulate horizons within layered basic intrusions and as components of the sub-oceanic mantle in obducted fragments of ocean crust known as ophiolites.
Subjects: Earth Sciences and Geography.