The U.S. Military patented a very expensive form of transparent aluminum back in 1980. In 1986 in Star Trek IV The Voyage Home, Scotty the ship’s Engineer shared a method of creating Transparent Aluminum with a company dealing with polymers. Here is that video clip:
Since then, there have been several varieties of a Transparent Aluminum and this is one of the most popular demonstrations that circulated the Internet:
A research team at the University of Tokyo’s Institute of Industrial Science has created a totally transparent glass, which is as strong as steel! It is much more advanced than what you see in the picture above.
Aluminum is already added to some glass to increase the strength, but the more they add, the more crystallized the glass looks. The breakthrough is that up to 50% aluminum can now be added and the glass is perfectly clear – and is as strong as steel and iron.
Go here for the story by Nature: http://www.nature.com/articles/srep15233
Here is a paper on this project by the University (in Japanese): https://www.iis.u-tokyo.ac.jp/publication/topics/2015/20151016press1.pdf