Botswana Diamonds (LON:BOD) latest drilling update from its joint venture with Russian giant Alrosa in Orapa was greeted with disappointment by the market.
Two of the three holes drilled intersected a different type of rock to other kimberlites found in the Orapa area.
There were significant Kimberlite Indicator Minerals (KIMs) in its core, but these have been taken by Alrosa back to Russia for full analysis adn identification.
John Teeling, Botswana’s chairman, said:" The good news is that the techniques used by our partners Alrosa have worked in this instance by delineating ultramafic rock, of which kimberlite is one type buried under 90 meters of sand.
“The rock discovered is not Orapa kimberlite but appears to be another older ultramafic rock.
“The core is now being processed to identify what it contains.
“Exploration on this block continues to identify the source of the two small diamonds we discovered in earlier work."
Shares fell 16% to 0.74p.