I've played through a half dozen times now and I recently sold a spell component and thought, "Wait, I've played this game a lot, how could I make that mistake?" I think the game could benefit from a way to easily identify the difference between:
If there isn't already a convenient way to identify each category (outside of hovering over each item), I would suggest a color coding system (e.g. red for spell, blue for crafting, green for treasure).
I could also make an argument for plot and faction items, but let's start with the more prevalent items first!