I think that a good idea for an element would be living organisms. I don't know what they could be used for but, think that they could be used to eat plant.

SerGreen

If we add plasma????

Reading all these posts, i think the only worthwhile ideas are:

1) antimatter
2) plastic
3) coal (it would have to be modified from what SerGreen said. Could it be made when wood or plant is put under pressure? It would also probably have a smaller volume than the amount of it made from wood/plant, a high ignition temperature and would burn with a fair amount of heat and would burn quite slowly. (though it seems as if we're running out of black element colours)

Macapple: If we add plasma????

I'm sorry, my English is not excellent
What does your question mean?

Maybe we could add a sponge, it absorbe all particles that it touch, and when there's pressure on it, all the particles get out of it. It's the smartest idea I had for now. I had the idea of meat but....it's kinda stupid.