What it is:
Fool's gold is a shiny mineral called pyrite which bears great resemblance to, and is often confused with, real gold.
How it works/Example:
Actually an iron-based mineral, pyrite is known for being yellow and shiny and appearing no different from real gold. But unlike real gold, fool's gold bears little, if any, intrinsic, social, or market value. Fool's gold has historically been found in mass quantities and mistaken for gold ore. Its name refers to those it "fools" into believing they have discovered a gold mine.