Going by the D&D weight of gold coins... I have 451 tons of gold
If I did the math right... that would make a solid gold cube 9ft on a side.
OR... 24.5 kilotons of silver for a cube of 42ft... or... 1.13 megatons of copper for a cube of 159ft.
The gold would be $16.7B IRL value. Sadly, nowhere near Scrooge McDuck's estimated worth of $65.4B (from Forbes 2013 report)