Glass does not have to be transparent. Just look at http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/ObsidianOregon.jpg/600px-ObsidianOregon.jpg
The Elder Scrolls glass is clearly not meant to be obsidian, though, seeing as obsidian is not green. And maybe the glass in glass weapons and armor really isn't supposed to be transparent, but if that's the case, why call it glass? It clearly doesn't have the same physical properties as glass, since it's practical to make armor and weapons out if it, so the only way the name could make any sort of sense is if it looks like something we might call glass. Now, it's true that glass does not necessarily have to be transparent, but I'm just saying, calling something glass is kind of misleading when it neither looks nor acts like what usually comes to mind when the world "glass" comes to mind.
The only thing that makes me think its elven is because the devs maybe wanted to show a whole set, so they pair elven armor with the elven sword. In another screenie, you can see the elven armoured PC with a mace on his belt, which I figure is an elven one.
That could be the case, but I don't think that alone is necessarily enough evidence to conclude that it's elven, now, I'm definitely not saying it's NOT elven, I mean, if it didn't look like something else, I might think that too, I'm just saying that if the design makes us think it's something else, than the fact that it's being used by someone wearing elven armor alone doesn't really prove anything.
In the trailer, when the guy shoots the ball of light in the cave, you can see that sword up close, since its equipped. Looks awesome.
Hmm, I never noticed that it was the same sword, I might have to watch the trailer again, or find a good screenshot of it to get a closer look.