Cut these slabs for lapidary recently.
Whenever you a see a rock with those little vugs full of translucent green crystals of forsterite/peridot/olivine you want to take a close look at it. From Michigan.

yeah, that was a cool one I've had sitting around for a while and finally cut. It looks like a dirty ol'rock until you cut into it. i kept a couple slabs but one person bought almost all of it. 
Any of those rocks with little vugs lined with little green crystals like that are usually worth cutting into. It's surprising though, there isn't a 'big' improvement after working and polishing. Those are fresh cuts and that's about as shiny as it gets.