Oh, not this rubbish again. Every few months, some reporter posts a story about this as if it were some miraculous new breakthrough, and they always have to use the "transparent aluminum" reference, the "gee whiz, it's just like that sci-fi movin' pitcher thingy!" hook that reporters can never resist even when it's a totally wrong and misleading analogy (which it usually is), and you get a new flurry of website posts saying "Hey, look, transparent aluminum is real now!" from people who don't remember the previous dozen times this "news" came out.
Here's the real scoop: It isn't "transparent aluminum." It's transparent alumina. Alumina is a compound containing aluminum, but it isn't aluminum any more than water is hydrogen or table salt is chlorine. It's a substance also known as corundum or emery (yes, it's the stuff coating an emery board). It's what rubies and sapphires are made of, so its transparency is nothing remarkable at all.
So this stuff isn't some miraculous transparent metal. It's a kind of glass, that's all. It's a strong kind of glass, but it's still just glass. Calling it "transparent aluminum" is misleading, pretentious, and wrong. It's as stupid as calling water "liquid hydrogen." You wouldn't call window glass "transparent silicon" -- you'd call it "glass," because that's what it is. And that's what this is. Alumina glass.