I suspect it's Olive Ash but would appreciate confirmation.
I do lot of wood id by looking at end grain under magnification. There are just too many species and variations within species to do a positive ID from the visual appearance in a photo of the side grain. Look at the incredible variation within some species on this site:
exotic wood ID site
hobbithouseinc.com
I don't have experience with Olive Ash.
You might read this article, especially section 7:
www.wood-database.com
Note also the "Still Stumped" section on how to get professional help.
Where did you get the wood? Knowing where it came from and where the tree grew helps a lot - locally grown? Bought from a wood dealer?
If unknown, there are simply too many species around the world that have similar appearance. For example, some Zebrano looks much like the piece you have.
Besides the end grain examination, other clues are density and smell. Having the wood in hand helps a lot.
Unfortunately, it is often easier to rule out a candidate species than to make a positive ID.
For more on wood ID I recommend the book "Identifying Wood" by R. Bruce Hoadley.
If you can't make a positive ID you might do what many do: write the name of what you think it might be on the back and never look back!
I once saw a bowl marked Cherry but the wood was definitely ring porous, even without a magnifier!
JKJ