硅けい板ばん岩がん

noun

Lydian stone; touchstone

Rare geological term for a type of siliceous rock historically used as a touchstone for testing precious metals. Mainly encountered in specialized literature.

• 硅けい板ばん岩がんはかつて金きんの純じゅん度どを調しらべる試し金きん石せきとして使つかわれた。

  Lydian stone was once used as a touchstone to test the purity of gold.