Oooh ... ahhh. This is petrified sequioa from Washington State. Pretty darn rare, and I love those little tree rings. I went to a gem show in Sedona and had a pretty good haul. Snagged this next beauty from the same gem cutter:
This has a ridiculous scientific name, but it's really hunks of junk peeled from the floor of a Mexican paint factory. It's then cut and polished as cabochons. They do something similar with the paint from car factories and it's called Fordite. Click to get the full effect of all those rich colors.