A student examines a small boulder of kimberlite remaining after the Triple-B kimberlite prospect near New Liskeard was backfilled by the propety holders - presumably to thwart further examination of this occurence of kimberlite intruding Paleoproterozoic argillite. Kimberlite is a dark, heavy, often fragmented igneous rock that may contain diamonds in the rock matrix.
(Images courtesy of Andrew Daly.)