psammiteyoudaoicibaDictYouDict[psammite 词源字典]
"Originally: †a fine or smooth-grained sandstone ( obsolete ). In later use: a sedimentary rock composed of medium-sized particles (commonly defined as those with a diameter between 1/16 mm and either 2 or 4 mm)", Early 19th cent. From French psammite from ancient Greek ψάμμος sand + French -ite.[psammite etymology, psammite origin, 英语词源]