This thesis examines power relations in the context of social impact assessment (SIA) as it is applied in the emerging mining industry in Solomon Islands. While the social impacts of large-scale mining in the Global South are well documented, little is known about how and why adverse social impacts continue to occur in the presence of numerous 'best practice' policy and planning tools, including SIA. This raises questions on the efficacy of SIA in identifying, contextualising and mitigating potential social impacts on communities affected by mining activity, particularly on traditional lands inhabited by indigenous peoples.This thesis presents a critical analysis of SIA to provide insight on this disparity in policy and practice, and to enhance sociological understanding on the interplay of globally-driven mining projects, the identification of social impacts, and the role of policy and institutions in cross-cultural contexts. The proposed extraction of nickel in Isabel Province, Solomon Islands, serves as the case study for this analysis. Employing the conceptual frameworks of social justice and political ecology, and drawing on six months' fieldwork in Solomon Islands, qualitative data from individual and group interviews (n=33) and document analysis (n=11) was collected across geopolitical scales -international, national, provincial and local -to compare and analyse perspectives of documents, institutions and people towards SIA and socially just development in the context of potential mining activity. Analysis of these perspectives exposed the extent to which SIA produces, reinforces and/or exacerbates, social injustices.Research findings identified the limits of SIA in: 1) recognising and accounting for indigenous identities and gender roles; 2) the unequal distribution of economic and other resources associated with the development of mining, including the privatisation of land and employment; and 3) representation of project-affected communities through consultation activities associated with SIA, including Free, Prior and Informed Consent. With political ecology as the foundation of this thesis, this thesis argues that these social injustices materialise as a result of a disparity, or mismatch, between knowledge frames across scales.While SIA is bounded to the rhetoric of social justice, consent and participation, this thesis demonstrates that Western expert knowledge and norms are interwoven into the SIA regime, rendering local experiential knowledge marginal. Reflecting this, a multiscale SIA approach is proposed to include consideration of different scales of knowledge systems, iii with outcomes that might assist to mitigate social injustices, such as those identified in this