I. ˈ ̷ ̷ˌ ̷ ̷ noun
1. : a black siliceous stone related to flint and formerly used to test the purity of gold and silver by the streak left on the stone when rubbed by the metal
holding out gold that's by the touchstone tried — Shakespeare
— called also Basanite, Lydian stone
2. : a test or criterion for determining the quality or genuineness of a thing
an original work is the touchstone that exposes educated taste masquerading as sensibility — Clive Bell
Synonyms: see standard
II. noun
: a fundamental or quintessential part or feature
among the touchstones of his conversation were terms like “discipline,” “craft,” “tradition” — H.L.Gates, Jr.
nor can one possess the work merely by studying the touchstone passages — Benjamin De Mott