EstablishedA grouping of chemical elements, sought as a group. Not an element.
The rare earth elements are a commodity grouping, not a chemical element. The group comprises the lanthanides together with yttrium and, by some definitions, scandium; they are sought, reported and traded as a group because they substitute for one another in the same crystal sites and are separated only with difficulty. Lithoen holds five of them as Element records with their own atomic numbers, and this record is a sixth thing: the commercial and geological concept that gathers them.
- precision note: The standing example of why commodity and element are separate entity types. Collapsing them would make "rare earths" a chemical element, which it is not, and would leave nowhere to record that the group is a market and processing concept as much as a geochemical one.
- precision note: Evidence corrected in Phase 6. This claim previously cited a single record, the porphyry copper compilation’s completeness note on which deposits it includes, which has nothing to do with the rare-earth elements. The entailment audit found it because the premise established no part of the assertion. It now cites the USGS rare-earth chapter’s own definition of the group, its account of why the elements travel together, its light/heavy division and its treatment of promethium.
Evidence support: Supported by the cited evidence one source
Evidence: Gosen 2017 Primary authority