Magic Pearl
A magical pearl that Glinda uses to detect lies; it turns black when falsehoods are spoken.
First named in The Marvelous Land of Oz, ch. 23
drew an immense white pearl, attached to a slender chain
What the books say it is
colour white 1 chapter
Only when the truth is spoken will my magic pearl remain a pure white in color.”
The Marvelous Land of Oz, ch. 23