Like uranium vis-à-vis carbon
I believe the answer is:
rarer
(Other definitions for rarer that I've seen before include "Less often seen" , "Stranger" , "even less common" , "less easy to find" , "More unusual" .)
I believe the answer is:
rarer
(Other definitions for rarer that I've seen before include "Less often seen" , "Stranger" , "even less common" , "less easy to find" , "More unusual" .)