"A good jeweler should be able to tell a real stone from a phoney one."
noun
°A person who assumes an identity or quality other than their own.
"He claims to be a doctor, but he's nothing but a fast-talking phoney."
°A person who professes beliefs or opinions that he or she does not hold.
synonyms:
bogus, counterfeit, fake, dissembler
more»
, pretender, fake