touchstone
noun
- piece of stone used in assaying precious metals
- metaphorical measure of truth
Wiktionary
Pronunciation: /ˈtʌt͡ʃstəʊn/
name
- A surname.
noun
Etymology: From touch + stone.
- A stone used to verify the quality of gold alloys by rubbing them in order to leave a visible trace.
- A standard of comparison or evaluation.
“Near-synonym: comparator”
“The foregoing doctrine affords us also a touchstone for the trial of spirits.”