So, it’s actually a thing – called ALON. It’s not so much a metal as an aluminum-based ceramic called aluminum oxynitride, but the point is, it’s aluminum, and it’s transparent:
and this stuff is strong – 1.6″ is enough to stop a .50 AP bullet that easily passes through twice that thickness of laminated glass armor:
aye, ol’ Scott woulda been proud. And just for old times’ sake:
Let’s take this opportunity to correct a misconception: they did NOT use transparent aluminum for the whale tank. They traded the “matrix” for it to the engineer at the large plate glass manufacturing place in exchange for enough conventional plate to build the tank. Which was a lot.