I don't know where you found this information, but it is totally inaccurate.
I suggest you read here:
http://uo2.stratics.com/questing/egwexem-and-naxatilor
Where you will find the instruction together with an image illustrating this action.
The sand you mentioned comes from
Niporailem The Thief a mini-boss encounter reached by a secret doorway from the Tomb of Kings, not related in any way to accessing or leaving the tomb itself.
I tried looking back in my history, but it's a mass of pages from google search, uoguide, stratics and others so no telling where I read it exactly sorry. Only thing I can think of that most of what I find from sites I've had to piece things together from more than a few pages to figure things out since the sites are hard to find things through their search engines, especially when a person has has no idea of the exact keywords or terms to use because it's all new. Well at least new to me, which is why I try to look up stuff and try to understand things from the help chat. Only page I found that mentions the gold turning to dust was this:
http://www.aschulze.net/ultima/guide/termur_dungeon_tomb.htm so I might have interpreted it as being a guardian that hinders those that don't say the correct passwords with gold that turns to dust lol.
As for the leaving of the area I never knew about that till I mentioned it in my 2nd post and got a reply from Popps. But I'm glad that you were able to set things straight and had a good link too!
I never saw that link with all my searching but I wasn't looking for specific names either since I never did those quests to get into the area. I'm just glad that overall Yadd finally got his answer along with more support and weight for that answer from others too! Thanks again!