What is it

[WDH]

I am settling on hickory too.  The bark is not scaly enough to be pecan/

[SwampDonkey]

Does hickory have narrow sapwood like the walnuts? The bark doesn't look like black locust, which is thick, interlocked and fibrous. I think black locust heart has a yellowish brown tinge.

No.

Well we've come full circle. Since my first post.

I just don't see the banding coloration in the bark for elm.

I'll never second guess myself again.

[woodtroll]

All right if not S. elm and its a hickory, I can't buy that it is pecan. To much dark heart wood. My first thought with hickory would be mockernut, http://www.forestryimages.org/browse/subimages.cfm?SUB=3266, shows some images. The dark wood throws me for mockernut, it tends to have a small heart.  I have seen pignut with a lot of dark wood but the bark is different.
The coloring of the wood pushes me back to S elm, even with out the string-e-ness.
I think I have reached the end of cyber deduction from a few pictures of firewood. 

[Brian Beauchamp]

It could be a black hickory, but I'm still leaning toward pecan because of this pic:



...and where is everyone getting that this has a really dark heartwood? Not really that much darker than the sapwood to me.

[Brian Beauchamp]

...unless this is from the same log in his gallery :

[Brian Beauchamp]

...but all of these look like they have much lighter-colored heartwood :

[roscoe234]

the upper picture was fresh split for this session....in the lower picture the wood had been split for several days......Pedro, the fellow who cut the tree down, told me originally it was some kind of maple.....ya dont spoze he's right?

[SwampDonkey]

Rings seem too distinct to be maple I'm familiar with. Looks rings porous.

[WDH]

Nope, not maple.  It is definitely ring porous.