Assertion: cerium | /r/HasProperty | produced as metal
Facets:
value: often
type: TEMPORAL
Source sentences:
text: Cerium and lanthanum as well as other members of the rare earth series are often produced as a metal called mischmetal containing a variable mixture of these elements with cerium and lanthanum predominating; it has direct uses such as lighter flints and other spark sources which do not require extensive purification of one of these metals.