The Fire Opal Mechanism by Fran Wilde (Tor.com June, 2019) 

Jewels and their lapidaries and have all but passed into myth.

Jorit, broke and branded a thief, just wants to escape the Far Reaches for something better. Ania, a rumpled librarian, is trying to protect her books from the Pressmen, who value knowledge but none of the humanity that generates it.When they stumble upon a mysterious clock powered by an ancient jewel, they may discover secrets in the past that will change the future forever.