A few levels into Hammerlorn mine, I found a room full of gold. The door was barred and I've found no way to get in. Is there any way to get the gold, or is just there as a prop of sorts?

I think it's just for show. I've never found a way into that room. In fact, I think the game text tells you that even if you could get in, there's no way you could carry off that much gold.

The 3 chests in there contain several gold bars and a diamond but the piles of gold are just floor decals and can't be collected.

Find the Crux of Fire and return to Korren. After Korren gives you a new quest, talk to Erubor and accept his quest to visit Lorewitch Tower. Complete Erubor's quest, and you'll be in possession of the Plasma Wand. Return to Hammerlorne Mine and use the Plasma Wand on the mithril gate!

And after you return to Hammerlorn with the plasma wand, don't forget to curse Jedi_Learner's skill with an image editor.

I read the post, and thought - yeah right... Then I looked at who posted it... *sigh* He gets me every time. If only if only...

EDIT: By the way though, if in the map editor you did remove the gate, the chests just random loot I assume, or is there even anything in them, or what?

Several people have edited themselves past the gates. They are just random loot.

So what have we got ... The trick with the broken gates of Mithril - impossible? Or is there, still, what is the path to these chests?

The chests are purely decorative, like the ones in several of the shops throughout the game.

Big thx.