Could be a lamproite....doubtful on kimberlite. Kimberlite has considerable garnet, and chrome diopside. Could also be simply a piece of lava that picked up other gravel as it came up. The residual heat is enough to keep it moving, but not enough to melt the gravel it picks up. I picked up a similar piece, but green/gray about 3 weeks ago. Interesting rock.
Jim