phenacite[fĕnˈə-sītˌ] or phen·a·kite [-kītˌ]
phenacite definition by American Heritage Dictionary
A natural beryllium silicate, Be2SiO4, occurring as vitreous crystals sometimes used as gems.
Origin: Greek phenāx, phenāk-, impostor + -ite1.
Variant of phenakite
a very hard, glassy, rhombohedral mineral, BeSiO, of various colors, sometimes used as a gem; beryllium silicate
Origin: Swedish phenakit ; from Classical Greek phenax (gen. phenakos), cheat plush -ite: from being mistaken for quartz