a translucent, usually greenish, mineral, sodium aluminum iron silicate, Na(Al,Fe)SiO, of the pyroxene group, found only in metamorphic rock, esp. in Myanmar: it is the most precious type of jade
See jadeite in American Heritage Dictionary 4
(jāˈdītˌ)
noun
A rare, usually emerald to light green but sometimes white, auburn, buff, or violet mineral, NaAlSi2O6, used as a gem and for ornamental carvings. It is the tougher and more highly valued form of jade.