Chalco-

From New Latin, from Ancient Greek χαλκός (khalkós, “copper”). Despite the appearance in English of a possible relation of chalco- to chalk, and any plausible semantic and cognate connections between limestones and ores in ancient times, the terms are not related by any known cognation. Note also the hard ch sound (/k/) in chalco- and words generated therefrom, which differs from the soft ch sound in chalk.