An Albeni meditation crystal was a large crystal which glowed with a white-yellow light when activated.
Commander William T. Riker presented one to Beata, the leader of Angel I, as a gift when the USS Enterprise-D visited the planet in 2364. (TNG: "Angel One")
The crystal prop later appeared in DS9: "Q-Less" as an embryonic lifeform from the Gamma Quadrant, which Quark acquired from Vash and then attempted to sell at auction.