Well here are two logs I split and took moisture readings on. Both come in at 14%. I got a half cord of this stuff for free this past June. It was sitting stacked on pallets and top covered for 2 years. It is rock hard. Doesn't hold a flame and just coals and coals away.
Could have got some chemical absorbed into it. Something preventing off gassing. Know wood type & when/where it came from?
That could be locust and sometimes it can be difficult to get it going. That is why some folks mix it with other woods.
Looks like black locust to me. Some people say you need to add it to a good coal bed to really get it going, but I've been burning a ton of it this year and have started many fires with some paper and kindling and never had a problem getting it going fast. You do have to give it more air than other woods...open it up a little and see what happens.
I burned a load of locust one cold night. It burns slower as its so dense but if I gave it air had flames or slowed it it would just coal and burn through it. I have a cat stove so I'm not wanting much flame anyway.
Now that we know it has trouble with a flame, which is ok, then you can make some choices on what to do. I like, as others have suggested, that it be mixed in with other hardwoods. It's still going to give off some decent heat and a long coal down time with it. With red and white oak when I burn, I get a flame, as dense as it is but I also get some of the best coals when the process gets to that. It's just a pain in the azz to dry...
looks like ancient locust (been dead for a while) and the fact that it lasts without much flame makes me thing so even more. could also be hophornbeam (ironwood), either way it's great stuff......I save my locust for overnight burns. If you are using it, it helps to mix a couple of splits of maple, ash, elm or even oak with it......helps it fire off better. But after a long burn, the only thing left in the firebox with that stuff is a heap of deep red glowing coals and lots of good heat.....