名詞 touchstone:

1. a basis for comparison; a reference point against which other things can be evaluated
   同義詞：standard, criterion, measure

1. As the touchstone tries gold, so gold tries man.
   試金之石可試金，正如黃金能試人。
2. The greatest touchstone of any work is time.
   時間是檢驗一切的最好的試金石。
3. Love is the touchstone of virtue.
   愛情是美德的試金石。