hy·per·sthene 
(hīpər-sthēn′)
(hīpər-sthēn′)n.
A green, brown, or black splintery, cleavable pyroxene mineral, essentially (Fe,Mg)2Si2O6.
[French hypersthène : hyper-, extreme (from Greek huper-; see HYPER-) + Greek sthenos, strength; see segh- in the Appendix of Indo-European roots.]
hy′per·sthenic (-thĕnĭk) adj.