touchstone
Concise Oxford English Dictionary © 2008 Oxford University Press:
touchstone/ˈtʌtʃstəʊn/
▶noun
- 1 a piece of fine-grained dark schist or jasper formerly used for testing alloys of gold by observing the colour of the mark which they made on it.
- 2 a standard or criterion.
'touchstone' also found in these Oxford entries:
