Class : Silicates
    Subclass : Inosilicates
    Crystal system : Triclinic
    Chemistry : X_n(SiO₃)_n
    Rarity : Fairly common to frequent

Pyroxenoids form a group of triclinic inosilicates, close to pyroxenes and whose chains of tetrahedra are twisted compared to those of pyroxenes. They too have a Si/O ratio of 1/3, like pyroxenes. Two pyroxenoids are important : wollastonite (CaSiO₃), mineral typical of skarns, formed in contact halos on limestones, by reaction of quartz and calcite, and rhodonite (MnSiO₃), mineral of metamorphic manganiferous deposits having undergone metasomatism, and certain hydrothermal deposits.

Main photo : Rhodonite from Morro da Mina, Minas Gerais, Brazil © Rob Lavinsky