Glass-ceramics and precursor glasses that are crystallizable to glass-ceramics are disclosed. The glass-ceramics of one or more embodiments include rutile, anatase, armalcolite or a combination thereof as the predominant crystalline phase. Such glasses and glass-ceramics may include compositions of, in mole %: SiO2 in the range from about 45 to about 75; Al2O3 in the range from about 4 to about 25; P2O5 in the range from about 0 to about 10; MgO in the range from about 0 to about 8; R2O in the range from about 0 to about 33; ZnO in the range from about 0 to about 8; ZrO2 in the range from about 0 to about 4; B2O3 in the range from about 0 to about 12, and one or more nucleating agents in the range from about 0.5 to about 12. In some glass-ceramic articles, the total crystalline phase includes up to 20% by weight of the glass-ceramic article.