Assertion: actinium's isotope | /r/AtLocation | nature as primordial nuclides
Facets:
value: as primordial nuclides
type: MANNER
Source sentences:
text: All these isotopes are stable and are also present in nature as primordial nuclides, but their excess amounts in comparison with lead-204 (which has only a primordial origin) can be used in the technique of uranium-lead dating to date rocks.