A glass-ceramic that includes a first crystal phase including (MgxZn1-x)Al2O4, where x is ≤1, and a second crystal phase including tetragonal ZrO2. The glass-ceramic may be substantially free of arsenic, tin, antimony, and cesium, each of the arsenic, tin, antimony, and cesium present at less than 0.01% (by mole of oxide). Further, the glass-ceramic may include a transmittance of at least about 80% to light having a wavelength of 380 nm to 760 nm.