J. Clarke wrote:

You don't say where you are--if you're in the US you could send Forest
Products Laboratories a sample and they'll identify it for you, at
least as far as can be done by examining the wood itself.
[...]
http://www2.fpl.fs.fed.us/WoodID/idfact.html

Thanks for the tip, I'll keep that in mind if I run into any more
mystery wood.