Pyroxene group minerals are found in both igneous and metamorphic rocks, and in a wide variety of meteorites. They may also contain calcium, sodium, and lithium. The pyroxenes have prismatic cleavage, and one can note the angle of 87° and 93° (almost perpendicular), which distinguishes them from the amphiboles which are at 56° and 124°. It may be confused with other pyroxenes or with hornblende, but the latter has two cleavages at 60° to each other. Pyroxene Group Minerals. It is a common primary mineral in basalt, gabbro and peridotite and a high-temperature metamorphic mineral in gneiss and schist. Augite, diopside, jadeite and spodumene are four of the best-known pyroxenes. Augite is the most common pyroxene, and its formula is (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al) 2 O 6. Augite is usually black, with stubby crystals. The photo to the left is representative of this mineral group; however, it is not the same sample on which spectra listed below were measured. Group of inosilicates that contain iron, magnesium, silicon, and oxygen. They occur in igneous and metamorphic rocks throughout the world. A large group of inosilicate (chain silicate) minerals with the general formula ABSi 2 O 6 . American Mineralogist, 94, 1479-1482. Pyroxene was originally what might now be called "augite", but the name has been raised as a group name of structurally and chemically similar minerals. Pyroxenes are members of a mineral group defined by a similar chemical compositions and crystal structures. Makoto Kimura, Takashi Mikouchi, Akio Suzuki, Masaaki Miyahara, Eiji Ohtani, and Ahmed El Goresy (2009): Kushiroite, CaAlAlSiO6: A new mineral of the pyroxene group from the ALH 85085 CH chondrite, and its genetic significance in refractory inclusions. February 27, 2018 Pyroxene Group Minerals 6 Hand Specimen identification: Association, form, two cleavages at 86° to each other, and color identify diopside .