Cedar Elm vs Pecan

[Pepe_Silvia]

I got a load of branches of these two mixed for firewood and I can't tell them apart.  Same with larger logs too - once the leaves come off it's hard for me to tell the difference.  Anything specific I can look that would allow me to identify which is which?

[Skipper11A]

The pecan will turn orange after a day or two of exposure to the air.  Cedar Elm will never turn any shade of orange, but will gray like a normal wood.

[LeeB]

Look at the end grain. Cedar elm will have a wavy grain to it. 

[WDH]

Lee is spot on.  The end grain of the two is very different, even to the naked eye.  You might need a razor knife to make a clean little slice to see the features clearly, but probably not.