A key issue with all mineral projects is the quantification of risk and uncertainty, which has always been narrowed down to grade estimation issues; however, just basing the mineral resource category on drill spacing and a competent person’s judgment on resource boundaries is no longer good enough. Rather, it should be statistically based, since juniors could not afford to undertake vast amounts of drilling, EY natural resource principal technical consultant Andy Clay said during the Joburg Indaba, held on May 21 and 22.