Pure CsPbBr₃ and CsPbI₃ perovskite nanocrystals are nucleated in the borogermanate glass. Nanocrystals precipitation in glass are controlled via isothermal treatment at temperatures above T_g by adjusting the temperature and duration starting from 15 min. X-ray diffraction data and optical measurements have confirmed the formation of 5–8 nm sized CsPbBr₃ nanocrystals and 6–15 nm sized CsPbI₃ nanocrystals. Wherein, the photoluminescence of lead cesium bromide perovskite is tuned in the 490–530 nm range, and the luminescence of iodide perovskite is changed in the 640–740 nm range. The maximum luminescence quantum yield of pure CsPbI₃ perovskites is 19%. Water, climate and acid resistance tests show borogermanate glasses with perovskite nanocrystals are compatible with commercial dense crowns.