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.

Beryllium silicate, a glassy transparent or translucent semi-precious stone that ranges in color from clear to pinkish to yellowish.

A glassy, colorless mineral occuring in rhombohedral crystals composed of beryllium silicate. From the Greek for imposter, deceiver, phenacite is a silicate of glucina, and receives its name from its deceptive similarity to quartz. It is sometimes used as a gemstone.