Well thwack, there's an old saying in the wide world of rock identification;
"If you aren't sure what it is, call it jasper."
My guesses would be rhyolite or jasper, but wyoming tiger stripe fits.
![Wink ;)](http://www.primitivearcher.com/smf/Smileys/default/wink.gif)
Might want to take a little flake off it and see how that goes.
Pretty piece.
Joe