Assuming your uncle is an amateur (otherwise, he would be using industrial methods), the only safe way of extracting gold is by gravity. The problem is that the gold dust is very fine, and may be too light to get trapped in a gold pan. It is a common misc

Pass a strong magnet over the sand to separate the remaining black sand. Black sand contains metal impurities that will stick to the magnet as it passes, leaving the flour gold on the paper. Remove the sands as they fill the magnet, repeating the process

Recovering fine gold from black sands is one of the most challenging aspects of gold mining. While we are all hoping to find that once-in-a-lifetime gold nugget, the vast majority of gold that we find as prospectors is very small in size, ranging from gol