There is mining permitted in certain PLACES - and mentoned, several times, in course of the story…Highscarp, and in Sethvir's earthlinked reviews, in Asandir's fleeting glimpse, as he leaves his body in TK…there are plenty of resources, with "add in" available for the future, via the gates…Mearth mined crystal and gems, which ARE very carefully handled on Athera.
Paravians were known to work both metal and stone.
The crystal Elaira picked up in the hedge healer's stall was not a proscribed stone.