T1O1U1C3H4S1T1O1N1E1
15 points
TOUCHSTONE is validvalid
[n TOUCHSTONES]
a highly siliceous (usually black) stone or other stone for testing gold or silver by the colour of the mark each makes on it; (figurative) a criterion, a standard [n -S]
[n TOUCHSTONES]
a highly siliceous (usually black) stone or other stone for testing gold or silver by the colour of the mark each makes on it; (figurative) a criterion, a standard [n -S]