Assertion: bohrium's rhenium | /r/HasProperty | one of the rarest elements
Facets:
Source sentences:
text: With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust.
text: Rhenium is one of the rarest elements in Earth's crust with an average concentration of 1 ppb; other sources quote the number of 0.5 ppb making it the 77th most abundant element in Earth's crust.