All that glitters is not gold

All that glitters is not gold is a well-known saying, meaning that not everything that looks precious or true turns out to be so. This can apply to people, places, or things that promise to be more than they really are. The expression, in various forms, originated in or before the 12th century and may date back to Aesop. The Latin is Non omne quod nitet aurum est.

Chaucer gave two early versions in English: "But al thyng which that shyneth as the gold / Nis nat gold, as that I have herd it told" in "The Canon's Yeoman's Tale", and "Hyt is not al golde that glareth" in "The House of Fame".

The popular form of the expression is a derivative of a line in William Shakespeare's play The Merchant of Venice, which employs the word "glisters," a 17th-century synonym for "glitters." The line comes from a secondary plot of the play, the puzzle of Portia's boxes (Act II - Scene VII - Prince of Morocco):

All that glisters is not gold—
Often have you heard that told.
Many a man his life hath sold
But my outside to behold.
Gilded tombs do worms enfold.
Had you been as wise as bold,
Young in limbs, in judgment old,
Your answer had not been inscrolled
Fare you well. Your suit is cold—
Cold, indeed, and labor lost.

Panning for gold often results in finding pyrite, nicknamed fool's gold, which reflects substantially more light than authentic gold does. Gold in its raw form appears dull and does not glitter. The expression is also found in Yiddish (nit als vos glanst iz gold), especially amongst Hasidim, and also appears in a Hebrew work of Mendele Mocher Sforim.

In pop culture, this phrase shows up in Bob Marley's "Get Up, Stand Up". It is also used as lyrics in the song "A Guided Masquerade" by Alesana, in the song "Domino Rain" by Antemasque, in the song "Gold" by Prince, and in the Kanye West song, "Family Business".

...
Wikipedia