X-ray opaque glass and its use

The invention relates to a radiopaque glass having a refractive index n of 1.48 to 1.56, which is free from at most impurities of SrO and PbO except for at most. The glass is based on the system SiO, AlO and BO. For the adjustment of the X-ray opacity, a combination of BaO, CsO and SnOin compound with fluorine is used. The glass can be used in particular as dental glass or as optical glass.