crucible, pot of clay or other refractory material. Used from ancient times as a container for melting or testing metals, crucibles were probably so named from the Latin word crux, “cross” or “trial.” Modern crucibles may be small laboratory utensils for conducting high-temperature chemical reactions and analyses or large industrial vessels for melting and calcining metal and ore; they may be made of clay, graphite, porcelain, or a relatively infusible metal.