Periclase
Pronunciation : Per"i*clase, Per`i*cla"site
Part of Speech : n.
Etymology : [Pref. peri- + Gr. (Min.)
Definition : Defn: A grayish or dark green mineral, consisting essentially of magnesia (magnesium oxide), occurring in granular forms or in isometric crystals.
Source : Webster's Unabridged Dictionary, 1913