Silicon

Silicon is a chemical element. When heated silicon can form glass.

Silicon-based lifeforms were considered a fantasy by the Federation until first contact with the silicon-based Horta of Janus VI in 2267 (TOS episode: The Devil in the Dark). In 2370, when Julian Bashir was attempting to locate a Horta in the mines of Davonia his tricorder had trouble singling it out as the mines had been drilled with high-powered phasers causing the walls to turn into glass, making the silicon lifeform difficult to detect amongst all the other silicon in the area. (DS9 novel: Devil in the Sky)