Meaning of touchstone

touch•stone

Pronunciation: (tuch'stōn"), [key]
— n.
  1. a test or criterion for the qualities of a thing.
  2. a black siliceous stone formerly used to test the purity of gold and silver by the color of the streak produced on it by rubbing it with either metal.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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