Abstract: Glasses containing fluorine. These glasses are characterized by the fact that they contain at least 25% in moles, approximately, of a fluoride or a mixture of fluorides MX(X.sub.1).sub.2, in which:X and X.sub.1 each represent a fluorine atom,and M then represents a metal chosen from among the group consisting ofgallium, iron, chromium, vanadium, indium, and the rare earths,or X represents an oxygen atom,X.sub.1 represents a fluorine atom,and M then represents a titanium atom, it being understood that the said glasses contain no hydrofluoric acid as a network former and that, in the case in which M represents a gallium or indium atom, the glasses do not contain more than 15% in moles of BaPO.sub.3 F.Application notably in obtaining glasses containing various cations conferring particular optical or magneto-optical properties.