Pyroxenite

Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite, diopside, hypersthene, bronzite or enstatite.

Purely pyroxene-bearing volcanic rocks are rare, restricted to spinifex-textured sills, lava tubes and thick flows in the Archaean greenstone belts.

This is in essence similar to the formation of olivine spinifex textures in komatiite lava flows, the chemistry of the magma differing only to favor crystallisation of pyroxene.

They frequently occur in the form of dikes or segregations in gabbro and peridotite: in Shetland, Cortland on the Hudson River, North Carolina (websterite), Baltimore, New Zealand, and in Saxony.

The rocks are often completely replaced by serpentines, which sometimes preserve the original structures of the primary minerals, such as the lamination of hypersthene and the rectangular cleavage of augite.

A sample of the orthopyroxenite meteorite ALH84001
Metamorphosed clinopyroxenite, made of green diopside, from the Shetland ophiolite , Unst , Scotland
Classification diagram for peridotite and pyroxenite, based on proportions of olivine and pyroxene. The pale green area encompasses the most common compositions of peridotite in the upper part of the Earth's mantle