Take a look at the following video, which details the excellent properties of transparent aluminum-based ceramic called aluminum oxynitride, aka “ALON".
(Transparent Aluminum Vs. .50-Cal Bullets)
Transparent aluminum starts out as a pile of white aluminum oxynitride powder. That powder gets packed into a rubber mold in the rough shape of the desired part, and subjected to a procedure called isostatic pressing, in which the mold is compressed in a tank of hydraulic fluid to 15,000 psi, which mashes the AlON into a grainy “green body.” The grainy structure is then fused together by heating at 2000 °C for several days. The surface of the resulting part is cloudy, and has to be mechanically polished to make it optically clear.
Star Trek fans of course remember a very similar notion from the fourth Star Trek movie, which aired in 1986. Take a look at this brief scene, which featured the most advanced computer available in that year.
(Star Trek transparent aluminum)
SF fans may also know that the idea of a transparent metal is much older. Olaf Stapledon wrote about an artificial transparent element in his 1930 classic Last and First Men.
I'd be remiss if I didn't also mention glassite from Ray Cummings' 1930 novel Brigands of the Moon and the helio-beryllium alloy that also had a transparent variant, as found in Out Around Rigel, a 1931 story by Robert H. Wilson.