Suppose you found a yellow piece of metal in a stream how can you tell if it's real gold

Hello!

The quickest and simplest way would be to take it to a jeweler or pawn shop and get it checked.

However, another way is: make a light, tiny scratch on the item using a small nail file or similar rough object. Choose a spot that is not noticeable if you want to keep it's value. apply a small drop of nitric acid to the scratch (use a dropper if you have one)

If there is no reaction, then the piece is probably made from real gold

I hope this helps, and have a nice day!