Elven Glass is more like a flexible transparent metal in characteristics than glass, and is forged rather than blown. However it retains many crystalline features as well and being transparent is considered ‘glass’.
In Celestia the Thelis are the first ones to work with this material. It is light and roughly as strong as iron, however you can see through it and it is a useful material to house crystals and gems used in magic. This makes it the perfect material for making into magical weapons like Rods, Staves, and Wands.
It is also the preferred material for making windows in fortifications as it won’t shatter like glass. The Ancients had stronger materials they used for windows, but few of those have ever been reclaimed intact and they cannot be recreated. Sadly the ores and chemicals to make this are fairly rare, so demand always outstrips supply.