This piece of kimbelite holds a sharp, undamaged diamond crystal, nicely exposed. The diamond is an octahedron with nice oscillating stria near the edges. I purchased this many years ago from Warren Boyd when he was importing diamonds from Russia. I could have chosen bigger diamonds in matrix but they were often damaged by whatever process they used to expose them. The kimbelite is textbook, showing small clasts of ilmenite, olivine, feldspar and, perhaps others. Very difficult to come by specimens like this and usually much more expensive! The proverbial "diamond in the rough".