Webster’s Revised Unabridged Dictionary · 1913
Phenacite
Phen′a·cite (fĕn′ȧ·sīt), n. [Gr. φέναξ, -ακος, impostor, deceiver.] (Min.) A glassy colorless mineral occurring in rhombohedral crystals, sometimes used as a gem. It is a silicate of glucina, and receives its name from its deceptive similarity to quartz.