Ruby Road – B.R. Kingsolver
The Crossroads contain the largest market in the known multiverse, and Diana Smith is a jeweler/smith who has a stall/storefront there. “Ruby Road”, like the first two books is a stand-alone novel, most of which takes place away from the Crossroads.
In this case, an untrustworthy old flame shows up with a small fortune in uncut rubies - and persuades Diana to help him find the mother lode. Diana has appropriate talents: She’s a world-walker, she can sense minerals, she knows how to use magical and mundane weapons. She’s also not too fussy about obeying inconvenient local laws.
It was a fun read.