I bought some XAUR and will keep it for quite some time. Can some one find proof that this token can be swapped for gold? There should be a clear proof that swapping can happen at near market price.
To keep them is a good decision, since growing gold base is increasing the coin value (price is determined on the market). To have gold coverage at the market price is impossible, since market price goes up and down and nobody can react as fast as market on selling and buying the gold (even if devs would have unlimited money supply to buy gold 
)Amount of gold behind every Xaurum is transparently shown on first page of https://xaurum.org/. Currently it is 1000 XAUR = 1.01577802 g/gold.
You can always swap Xaurums for gold here: https://xaurum.org/en/details/melt
Did you already tried to melt Xaurums?