Marine diamond mining as practiced on the west coast of southern Africa is considered to be a high-risk venture. Investment decisions can be eased by using simulations to model likely outcomes. This study utilised Net Present Value (NPV) to measure the impact of sampling and grade estimation decisions on a marine diamond mining project. It focused on aspects such as the accurate determination of geological conditions, the influence of the degree of error in the geostatistical estimation process, sample density and sample support size. A simulated deposit was constructed that could be sampled using various parameters to measure the sensitivity of NPV. Various scenarios and their related NPV's showed that exploration costs have a small impact on a project in comparison with other cost aspects. However, the decisions made in the exploration process do have a significant impact on the NPV of a project. Inaccuracy in recovery efficiency and mining rate prediction, lead to a decline in NPV. Misfitting the semi-variogram model had a smaller impact on the NPV than the other scenarios investigated, but the importance of reflecting the true variance of the deposit in financial terms was evident. Finding the optimal sampling density and support size do have a positive effect on NPV. It is believed that the method demonstrated in this study can be used as a guide to add value in the selection of optimal parameters when planning exploration campaigns in marine mining projects. AFRIKAANS : Mariene diamant ontginning, soos beoefen aan die weskus van suidelike Afrika, is 'n hoe risiko ondememing. Beleggings besluite kan vergemaklik word deur simulasies te gebruik om moonlike resultate te modeleer. Hierdie studie het Netto Huidige Waarde (NHW) gebruik om die impak van steekproefneming en skattings besluite op 'n mariene diamantontginning projek te meet. Aspekte soos die korrekte bepaling van geologiese kondisies, die invloed van foute in die geostatistiese skattings proses, steekproef spasieering en steekproef grootte, is ondersoek. 'n Afsetting is met 'n simulasie geskep. Steekproewe is dan geneem van die afsetting om NHW sensitiwiteit teenoor verskeie parameters te meet. Verskeie scenarios en hulle verwante NHW's het gewys dat, in vergelyking met ander kostes, eksplorasie kostes 'n klein impak op 'n projek het. In teenstelling hiermee is die impak van besluite wat geneem word in die eksplorasie fase groot. Onakkurate herwinnings effektiwiteit en ontginningstempo skattings lei tot 'n afname in NHW. Swak modelering van die semi-variogram het 'n kleiner invloed op NHW, maar die belangrikeid daarvan om die ware variansie van die afsetting te reflekteer, was duidelik in finansieele terme. Die gebruik van optimale steekproef spasieering en grootte het 'n positiewe impak op NHW. Die metode wat gedemonstreer word in hierdie studie kan gebruik word as 'n gids om optimale parameters te selekteer wanneer eksplorasie programme beplan word vir mariene diamantontginnings projekte. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Geology / unrestricted