This paper describes a software tool and its application to the China National Mineral Resource Assessment Initiative (CNMRAI). The initiative was carried out throughout China from 2007 to 2013, creating collaborations among geological societies from institutions such as academies, universities, companies, and local geological surveys. A geographic information system (GIS)-based tool was designed, providing functions for database management of the multiple original spatial datasets, modelling, targeting, estimation, and visualization to assist participants in assessing mineral resource potentials. During this initiative, geologists used the tool to generate mineral potential maps and assess undiscovered resources for the 25 major types of mineral resources in China. First, the requirements of the tool were introduced; second, the framework and major functions of the tool were delineated and developed; and third, a case study of gold resource assessment from a project of the CNMRAI in the Bayan Obo region, Inner Mongolia, China, was discussed. In addition, the mineral potential map was displayed by terrain rendering. This paper also provides interpretations of the results of a prospectivity analysis based on conceptual geological models. Discussions of the new requirements and techniques for modelling and assessing will be used to further develop the Mineral Resources Assessment Software (MRAS).