Germanium monosulfide
Germanium monosulfide or Germanium sulfide is the chemical compound with the formula GeS. Germanium sulfide is a red-brown powder or black crystals. It hydrolyzes slowly in moist air but rapidly reacts in water forming Ge(OH)2 and then GeO. It is one of a few sulfides that can be sublimed under vacuum without decomposition. It also forms chalcogenide glasses and is a semiconductor.