Mining exploration group Goldstone has received a notice of termination from Randgold Resources in relation to their joint-venture over the Sangola license in Senegal.The west and central Africa-focused outfit is listed on AIM, which is part of the London Stock Exchange. The group has various exploration projects in those regions.On February 18th, GoldStone - which partnered with Randgold on that Senegal project - announced the drilling programme on the Baraboye and Ibel prospects, which are a part of Sangola, did not justify an immediate follow-up programme.The shares promptly plummeted 15% on the occasion.As of 14:17 the share price dropped a further 19% to 0.6pWS