It is organic.
Beyond that, I am clueless. While I'm fairly sure that it was/is/fell off of/was excreted by something alive, whether it was animal or vegetable is a mystery.
This normally would not bother me, except that this sucker is practically welded to the deck. It's been there for at least a week, and has not loosened. It is attached.
It resembles a large, slightly ovoid walnut. It is covered in a dry, leathery substance that cracks like paper when poked with a broom. (I have not touched it--I SAW Alien thankyouverymuch.) The bottom side is cemented firmly down with a dark substance that may be insect poo or rotted fruit bits or fungal slime or god knows what. It is no particular color, and resembles the drab grey-tan of many other generally uninteresting thingies.
It is sitting in solitary majesty, alone on the recently swept boards of the deck.
I suspect it's an egg case or a chrysalis of some variety, but it could as easily be a particularly determined fungus, dead fruit, or piece of poo from a low-flying manatee. It is a mystery. In my heart of hearts, I know that it is an egg case for the Giant North Carolinian Giggling Razor Centipede of Death, which will emerge in the night, come into the house, and chase me around the room, whooping like an insectile hyena. However, I am willing to entertain alternate explanations. Anybody know what the heck these things are likely to be?