On Transparent Aluminum From Wikipidea

Aluminium oxynitride or AlON is a transparent polycrystalline ceramic with cubic spinel crystal structure composed of aluminium, oxygen and nitrogen. It is currently marketed under the name ALON by Surmet Corporation. ALON is optically transparent (≥80%) in the near-ultraviolet, visible and midwave-infrared regions of the electromagnetic spectrum.

Combination of optical and mechanical properties makes this material a leading candidate for lightweight high-performance transparent armor applications such as bulletproof and blast-resistant windows and for many military infrared optics. AlON based armor has been shown to stop multiple armor piercing threats of up to 50 cal.