Definition of "touchstone" []

• 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. (noun)
• 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. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Situated alongside the River Thames, the iconic power plant has been featured in works by The Who, Pink Floyd and The Beatles, and now this cultural touchstone is being retrofitted into a self-sufficent community powered by a zero-carbon energy plant."
• "Harry and Sally bicker over Casablanca; for the women of Sleepless in Seattle, the emotional touchstone is An Affair to Remember (“Men never get this movie!”)."
• "Its touchstone is the autonomous individual celebrated by John Locke in"