That's a Reagent for Spell casting. Click that thing next to your Mana whacker, and talk to the middle guy in the Haven Store if you have no spell books.

There are 10 kinds of reagents, the final 4 (Battlestar Galactica?) are supposed to be very rare, even buy only (or obtainable with the 20 max loophole), but I won a Monkey Fur the other day. Now if only I could get rare Emeralds or a Diamond instead.