Unstable Greater Burnished Essence

Unstable Greater Burnished Essences are what remains of Greater Burnished Essences, which can no longer be crafted. Prior to Shadowlands, using this item "restored" it into a Burnished Essence and 25 Sorcerous Water.

Source
The original version of this item, Greater Burnished Essence, was crafted by leatherworkers with a skill level of 1. The recipe was learned from Recipe: Greater Burnished Essence, which could be purchased from the Tannery at Lunarfall or Frostwall, or from the leatherworking vendor in Stormshield or Warspear.