touchstone

[ tuhch-stohn ]
/ ˈtʌtʃˌstoʊn /

noun

a test or criterion for the qualities of a thing.
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.

Origin of touchstone

First recorded in 1475–85; touch + stone
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for touchstone

British Dictionary definitions for touchstone

touchstone
/ (ˈtʌtʃˌstəʊn) /

noun

a criterion or standard by which judgment is made
a hard dark siliceous stone, such as basalt or jasper, that is used to test the quality of gold and silver from the colour of the streak they produce on it
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012