The Lump of Coal is attained by unboxing a boxed coal. Boxed coal is attained by unwrapping the Poorly Wrapped Gift from Bob. The present's description was "It's probably coal", granting a completely dead giveaway to what would be inside. Despite what is inside, it's still a rare item which was only available December 25th, 2015. For now, this item serves no purpose, other than decoration or collector purposes. It seems that it won't be coming back for future Christmas events. The gift is very small as it is sometimes hard to find. Learn more about coal here.Template:HeadingA
If you put the coal in the volcano tunnel entrance in the zone where red particles come out of the ground, (not in the lava) and wait for about 10-15 minutes the coal will be red with fire coming off of it. You will see the coal ignite immediately. If the boulders and music change has not been triggered, you are not taking damage, your coal is not far enough into the tunnel. Coal makes a great fireplace, or just lighting for your base, and also for decoration. It will cool down after a minimum of 10 minutes.
Leaving the coal in the tunnel for 30 minutes will give you 6 hours of burn time. However if left long enough, the coal can stay lit anywhere between 2-4 days.