This page details where you can find Uncut Gemstones in Eitri, Svartalfheim, part of the Dawn of Ragnarok DLC in AC Valhalla. There is only one Uncut Gemstone to be found in this region.
Uncut Gemstone - Southwest Maekinn
You’ll find this Uncut Gemstone just southwest of Maekinn, in southern Eitri. You’ll find it in a box in some ruins here, as shown in the screenshot below.