pyroxene

Any one of a group of minerals, silicates of calcium, iron, and magnesium with a general formula X,YSi₂O₆, found in igneous and metamorphic rocks. The internal structure is based on single chains of silicon and oxygen. Diopside (X = Ca, Y = Mg) and augite (X = Ca, Y = Mg,Fe,Al) are common pyroxenes.

Jadeite (NaAlSi₂O₆), which is considered the more valuable form of jade, is also a pyroxene.