When you put an ore in a furnace it is supposed to have either no image or a sort of transparent image of the ore (can't remember which one) in the output slot.

Instead it shows the image of an ingot (before it has actually cooked) and when the first one does cook it remains the same (shows image of ingot in the output of a furnace)

It does the same for cobblestone, iron ore and gold ore. Not tested the other items that you use in a furnace

Steps to reproduce:
Just try to cook anything in a furnace.

I'm using a HTC Desire C