A new class of sulfide glasses based upon the BaS–Ga 2S 3–GeS 2 system has been investigated. Glass compositions were prepared in graphite or vitreous carbon crucibles, encapsulated in silica ampoules, and cooled from a melt temperature of 1000°C. These glasses have good glass stability, with T x− T g in the range of 100 to 200°C, glass transition temperatures between 400 and 500°C, and infrared transmission to wavelengths of about 12 μm. Thermal, optical and mechanical properties of these glasses are reported and the effects of materials purity and processing on these properties are discussed. Their thermal stability and optical transmission band make these glasses candidate materials for rare earth doped lasers and fiber amplifiers, infrared fiber sensors and optical components for infrared systems.