phenacite

A natural beryllium silicate, Be₂SiO₄, occurring as vitreous crystals sometimes used as gems.

A rare mineral occurring in transparent rhombohedral crystals, colorless to wine-yellow, and having a vitreous luster.

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.

A clear glassy mineral, a silicate of glucina, occurring in rhombohedral crystals and sometimes used as a gem.