Jewelcrafting (often shortened to JC) turns precious metals and gems into rings, earrings, and necklaces. Because gems are mostly gathered from mineral veins, Jewelcrafters tend to also pick up Mining.
You’ll need a Jewelcrafting Kit or Trainee’s Jewelcrafting Kit to get started. In Night Harbor, find the jewelcrafting trainer to learn the skill, then visit a jewelcrafter in the Night Market to buy your kit. In Faelindral, Vaelyndir the Jewelcrafter can set you up as well.