My weekend at CalPaleo 2011 had a good share of thrills, but I think this one may have the most appeal to most of you: I put my hands on one of Earth's oldest rocks, the 4-billion-year-old Acasta Gneiss from northern Canada. It was in Sierra College's wonderful rock walk outside the meeting room. Good old gneiss may be Earth's most distinctive rock. I never used to think much of it because it has no fossils and is difficult to study, but I'm warming up to it as time makes me more metamorphosed.
Acasta gneiss Geology Guide photo