Iara dropping an unknow item and i cant sell "Mirror Crystals" in NB

Hello, Brasilis just arrived in the game and i was leveling in Brasilis Dungeon (Iara respawn) and after a few hours i looted an "Unknow Item" (screenshoot). I also looted few Mirror Crystals and Witherless Roses and tried to sell them. However i was able to sell only the roses (screnshoot 2). I would like to know if this is a bug or a regular feature.

Unknow Item


Cant sell Mirror Crystal