At long last the hungry plough man cheats, with empty grains instead of lusty meats.
In other words it produces something that looks like gold, but does not pass any tests.
I read just recently that tungsten has the exact same density as gold, meaning it will pass the test of volume to weight ratio.
If you created tungsten bars slightly smaller than the gold you were emulating, and coated them in 1/4 inch of real gold, it would pass even the most advanced testing including x rays. Nobody would suspect a thing without severely altering the bar,by cutting,drilling or melting it.
The counterfeits would be expensive to produce,considering their actual gold content, but it would be a long time before anyone suspected anything,maybe never.