Any ideas on what this is?

[TKehl]

Definitely try the magnet test.  That will tell a lot quick and easy.

I don't work in a scrap yard, but do run a metallurgy lab.  When asked how big, I show them a bit that is half the size of a BB and say that I can work with smaller, but it is fast and easy if it is at least that big. Then I can use the handheld gun instead of the scanning electron microscope. 

I doesn't harm the sample to take a surface reading.  You shoot it with some X-Rays and the meter looks for the energy decay signature to determine the element(s).  (I mostly work with alloys.)  Takes about 5 seconds for most metals.  If I have to grind/polish to get through rust, carbon, etc. to get to metal, that is the only harm done.

[markdvsmo]

Meteorite!

(I'm only half kidding.  Could happen.)

[Nomad]

     One of the first things I did was check it with a very powerful magnet.  It is non-magnetic.  Sounds like it's plenty big enough to test it.  No way this thing was ever fired from a gun.  Much too hard, and the shape is all wrong. 
     Non-magnetic, barely reads on a metal detector, black, too hard to scratch with a file...  I'm wondering if it could be a piece of stone?  Shattered on three sides and the rest is a rounded surface, like the tooth of a gear.  Would be an oddly shaped stone, but possible I suppose.  Or maybe a piece of ceramic?  I'm mystified.

[Chuck White]

If the piece you were resawing had been in a welding shop or was loaded on a truck or trailer, it could possibly be a piece of welding slag!

When a welder was chipping away some of the slag, it could have launched some distance and then being hot, imbedded itself into the wood!

Just a little thinking "outside the box"!  :

[Nomad]

Chuck, that's as good a theory as anything else I've heard, or come up with myself. :D

[Nomad]

    I believe I've figured it out. 8)  It is a piece of stone.  A piece of flat, water eroded stone like you'd skip across a creek or lake.  The profile matches perfectly.  How it got there?  I dunno.  Maybe the timber got dragged across some, or run over by a truck or something.  Need to find a mineralogist to verify that.

[Normang]

Roswell??

[Nomad]

Roswell??

:D