Sun-Glass is the special glass used in Argentum to contain lava. The glowing lamps, and the lit tubing that carries Everfire through the maintenance tunnels and the river, are made with it.1 The patrol lanterns of the Order of the Lantern are made of Sun-Glass.
Making
Sun-Glass is made by a mix of alchemical glass tempering and the blessing of the Silver Flame, so it could not have existed before the Starfall.1
History
Session 11
In the sealed vaults beneath the Silver Archives, Luma read graffiti claiming that the Everfire burned strong while a moat was frozen. Hazel pointed out that the old dwarven pipes in the foundries had no glass, and Luma knew from her past work that the glass lamps and tubing are new.1