hardpan
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Like any wood, it needs good drying, then it is rocket fuel. The inner heartwood down near the roots is what fatwood is, or the best anyway. Doesn't need drying and won't rot for years and years, no idea how long. That stuff you can light while it is wet with a match and it will catch and burn. Just some slivers carved off with a knife will get a fire going.
I have also heard it called pitchwood. I only tried it the last couple years and it performs exactly as you describe. I have fun throwing an average sized piece of it on a campfire and watching everyone pull their chairs back away from the fire, hot stuff. I find it in the big roots near the trunk also. Not much pine here though.