fool's gold
1. A mineral that resemble golds, such as pyrite. I used to dig up fool's gold all the time as a kid.
2. By extension, something that seems more promising than it really is. Don't invest in his latest wacky invention—no matter how great it seems, it will end up being fool's gold like all the others.
fool's gold
COMMON If a plan or something you want to achieve is fool's gold, it seems good but in reality is not likely to be successful or of good quality. ID cards are fool's gold. Their only use would be to identify the victims of the next disaster. All we wanted was an honourable settlement. He chose to go after fool's gold and lost. Note: Fool's gold is another name for iron pyrite, a gold-coloured mineral that is found in rock and that people sometimes mistake for gold.
fool's gold
something deceptively attractive and promising in appearance. Fool's gold is the name popularly given to any yellow metal, such as pyrite or chalcopyrite, that may be mistaken for gold.
2003 Nation Many good people have been euchred into falling for the current fool's gold—politicians and lobbyists calling for ‘universal healthcare’.