Ancient Nordic Pickaxe

 is a One-Handed weapon found in Solstheim. It is the only kind of pickaxe that can be used to mine Stalhrim. While it can be enchanted, it cannot be improved with smithing.

Retrieve the Ancient Nordic Pickaxe
Glover Mallory, the blacksmith in Raven Rock, will say that it was stolen by Crescius Caerellius at the mines and asks that it be retrieved. Once it is returned, he will let the Dragonborn keep it.

Other locations

 * There may be one in the ruins of Fort Frostmoth.
 * The smith of Skaal Village, Baldor sells them.
 * One may be in Miraak Temple Sanctum.
 * One may be at Northshore Landing in a (novice) locked chest or in a chest under the waterfall.
 * Might spawn randomly in the Damphall Mine North of Bloodskal Barrow. At the very end of the mine there is a Lord Reaver that holds a key to the (master) locked treasure room where it may be located.
 * One has also been found in the chest at Usha's Camp.
 * One may spawn in Vahlok's Tomb, in the chest in front of the Word Wall.
 * In Benkongerike cave on North part of Island.  In chest under Word Wall for Cyclone.

Variants

 * Hoarfrost - A unique variant held by Ralis Sedarys. It can be obtained via Pickpocketing, or completing the quest "Unearthed" upon which Ralis can be recruited as a Follower, if spared, and the Pickaxe can be taken from his inventory.