Gold mode

I tested gold mode on my $10 eagle, a 1/2$, and a dime. I used a chunk of iron that’s the size of the 1/2 dollar. If I place the chunk of iron side by side with the coins the gold mode picked up all coins. If I placed the chunk of iron on top of the coins the gold mode reads the silver coins as iron but surprisingly reads the gold coin with a higher VDI.