py·rox·ene 
(pī-rŏksēn′)
(pī-rŏksēn′)n.
Any of a group of crystalline silicate minerals common in igneous and metamorphic rocks and containing two metallic oxides, as of magnesium, iron, calcium, sodium, or aluminum.
[French pyroxène : Greek puro-, pyro- + Greek xenos, stranger (originally viewed as a foreign substance when found in igneous rocks); see ghos-ti- in the Appendix of Indo-European roots.]
py′rox·enic (pī′rŏk-sēnĭk, -sĕnĭk) adj.