a vessel for melting or calcining (reducing, e.g. to powder; see calcine) a substance at a very high temperature

a severe test

During the next half-century and more, my race [black people] must continue passing through the severe American crucible — Booker T Washington

a situation in which interacting influences produce something new

the encounter between the Arts and Crafts movement and pre-Raphaelitism that was the crucible of Art Nouveau