Ariégite is a pyroxenite chiefly composed of clinopyroxene, orthopyroxene, and spinel, with pyrope and/or hornblende as possible accessories and lacking primary feldspar. The type rocks were described by Lacroix (1901, 1917), occurring as layers in Iherzolite at Ariége, and elsewhere in the Pyrenees (Kornprobst and Conquéré, 1972). The particular rocks described by Lacroix have a mineral assemblage of diopside, bronzite, green spinel, and garnet. The term is still widely used in Europe, particularly by French geologists: in the IUGS nomenclature (Streckeisen, 1976) it would be termed diopside-bearing spinel pyroxenite or websterite (denoting a two-pyroxene rock). The absence of olivine distinguishes it from lherzolite, and the composition of the pyroxenes distinguishes it from eclogite.
Kelyphitic reaction rims, especially around garnet, are the rule in ariegite, the rims consisting of complex intergrowths that may include spinel, anorthite, pyroxene, or amphibole. They result from the...
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