subterranity

noun

1. An underground place“[…] as we may conceive in ſtones and gems, as Diamonds, Beryls, Saphires and the like, whoſe generation we cannot with ſatisfaction confine unto the remote activity of the Sun, or the common operation of coldneſſe in the earth, but may more ſafely referre it unto a lapidificall ſuccity, and congelitive principle which determines prepared materials unto ſpecificall concretions. And therefore I fear”