We’ll end the work week with a deskcrop of kimberlite breccia. Kimberlites, of course, are the type of rock that most commonly hosts diamonds. Unfortunately, I don’t think I’ve got any in this sample. This deskcrop comes from the Lake Ellen Kimberlite in Michigan’s Upper Peninsula. To the best of my knowledge no macroscopic diamonds have been recovered from this locality, however diamonds are known from the glacial drift south of here in Wisconsin. As I recall, a few xenoliths of garnet-bearing peridotite were found by our group at this locality, suggesting a depth of origin suitable for diamonds, but they were relatively scarce, and I’m pretty sure most of the breccia fragments in this sample are of a crustal origin.
Explore this and all of my 2010 Deskcrops and Outcrops in Google Earth!