Glass

Glass was a generic term for any molten silicon which could be naturally occurring (volcanic) or man-made and was, by definition, very fragile. Glass was most commonly used in windows, corrective lenses, and drinking es.

On Admiral Kirk's birthday in 2285, Doctor McCoy gave him a pair of reading glasses. The glasses later were broken in a battle with the USS Reliant commandeered by Khan Noonien Singh. The glasses were sold in 20th century Earth at an antiques dealer in San Francisco who purchased them for US$100, noting they would have been worth more if the lenses had been intact. 

An invidium contamination aboard the USS Enterprise (NCC-1701-D) caused a drinking glass to melt in the hand of its holder, Lieutenant junior grade releasing the beverage from within. 

"Glass" was one of numerous words Doctor Julian Bashir randomly used after he was infected by the aphasia virus in 2369. 

One form of glass was Tabalian glass. 

After she was beamed aboard the USS Enterprise (NCC-1701-E), Lily Sloane was surprised to see no glass covered a hatch to space. Jean-Luc Picard then demonstrated the function of a force field to her.