Definition Of touchstone
a piece of fine-grained dark schist or jasper formerly used for testing alloys of gold by observing the color of the mark that they made on it.
Small black stones were used as touchstones to test the colour, and hence purity, of gold.
Example Of touchstone
An article in a foreign journal becomes a touchstone and then a norm, unless it is torn asunder by some path-breaking discovery.
‘To touch’ in reference to fine metals such as gold refers to the touchstone used to test the purity of the metal.
But these terms, profoundly limiting as they are, are actually touchstones that disputants in the periodical debate would recognize.
By the Second World War the toleration of COs had begun to be recognized as a touchstone of mature liberalism.
Considerations on the French Revolution would become a touchstone for the liberals under the Bourbons.