I’m familiar with Russian olive although I haven’t burned it. This is definitely not olive. I think your right I think it’s red elm. Thanks for the help.I'm in your general area - Russian olive and red elm are very common in this low rain mountain desert climate. It isn't Russian Olive because Russian Olive has 'flaky' bark and a more tannish chocolate colored wood color.
So I'm going with Red Elm. If you split some, the fibers kind of want to hold together - but Red elm is suppose to be easier to split than the other sub species of elm, and it has a little higher btu rating, too. Also, you can see a slight reddish/violet hue in the brown part of the split wood. And, the tree usually has several branching parts in its growth - so the main trunk will go up 6 to 8 feet and then there will be 3 or 4 medium sized trunks coming off this main trunk.
A dead ringer - if the bark is removed and the exposed wood has little pointy nipples sticking out here and there - it is for sure red elm. I think it is in the area of 19-21 btu rating - so like walnut or cherry.