Assertion: cerium | /r/HasProperty | grey lustrous metal
Facets:
Source sentences:
text: Cerium is a grey lustrous metal that is malleable, and one of the most reactive of the rare-earth metals, also called lanthanides.
text: Cerium is a silvery grey lustrous metal that is malleable—it is soft enough to be cut with a knife, and tarnishes when exposed to air.