Yesterday Kite (9 weeks) took a lump of coal to play with. I thought she was just knawing on it a bit and batting it around, but found the lump was a lot smaller and no trace of the rest (she was in a pen, so couldn't have hidden it), so she must have eaten it. A kitten I used to have made quite a point of eating coal (and licorice too) when growing. It's obviously a good source of carbon and probably other minerals, and it hasn't done any harm to Kite or the cat, although it's not something I shall be encouraging.
Anyone else's pets eating fossil fuels?