It's just a name. They are not necessarily rare. It should be "certain transition metals", but transition is not what it seems in regard to "changing" in the common sense, either. So, certain metals, it is.

It's just a name. They are not necessarily rare. It should be "certain transition metals", but transition is not what it seems in regard to "changing" in the common sense, either. So, certain metal ores, it is.

It's just a name. They are not necessarily rare. It should be "certain transition metals", but transition is not what it seems in regard to "changing" in the common sense, either.

"Rare-earth" means lanthanides plus scandium and yttrium. But scandium and yttrium are not used in magnets, so they would confuse people less by saying "lanthanide magnet" instead of "rare-earth magnet".