Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio.
- a type of black stone formerly used to test the purity of gold or silver by the streak left on it when it was rubbed with the metal
- any test of genuineness or value
Used by arrangement with John Wiley & Sons, Inc.
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
- A hard black stone, such as jasper or basalt, formerly used to test the quality of gold or silver by comparing the streak left on the stone by one of these metals with that of a standard alloy.
- An excellent quality or example that is used to test the excellence or genuineness of others: “the qualities of courage and vision that are the touchstones of leadership” (Henry A. Kissinger). See Synonyms at standard.