Class : Silicates
    Subclass : Inosilicates
    Crystal system : Monoclinic
    Chemistry : (Ca,Na)(Mg,Fe,Al)Si₂O₆
    Rarity : Uncommon

Omphacite is a complex clinopyroxene, a solid solution of jadeite (25% to 75%), augite (25% to 75%), and aegyrine (0% to 25%). It is a pyroxene characteristic of very high pressure rocks, in the metamorphic domain (eclogites, of which it is one of the essential components) or magmatic (kimberlite); it is also present in certain ophiolites as well as in glaucophane schists and amphibolites. It is a companion of garnet and kyanite, less frequently of glaucophane. Its name comes from the Greek omphaz or omphaos (green grape) thus emphasizing its color. Omphacite is generally massive or granular, its crystals are rare and not very distinct (up to 5 cm). Its color is green to dark green; in this second case the omphacite sometimes takes the name of chloromelanite (but this variety is not restricted only to the field of composition of the omphacite). Neolithic omphacite adzes, although rare, were unearthed during prehistoric excavations in Brittany. These discoveries probably mean that these primitive peoples valued the eclogite blocks which dot Vendée and Léon in the Armorican Massif. It is sometimes used in ornamentation, particularly in China.

Main photo : Omphacite of Iveri, Aosta Valley, Italy © Franco Luca Bonino

No twin known for this mineral species.

No fakes listed for this mineral species.