This paper shows how ethnic identities may become more salient due to natural resources extraction. We combine individual data on the strength of ethnic-relative to national-identities with geo-localized information on the contours of ethnic homelands and on the timing and location of mineral resources exploitation in 25 African countries, from 2005 to 2015. Our strategy takes advantage of several dimensions of exposure to resources exploitation: time, spatial proximity, and ethnic proximity. We find that the strength of an ethnic group identity increases when mineral resource exploitation in that group's historical homeland intensifies. We argue that this result is at least partly rooted in feelings of relative deprivation associated with the exploitation of the resources. We show that such exploitation has limited positive economic spillovers, especially for members of the indigenous ethnic group; and that the link between mineral resources and the salience of ethnic identities is reinforced among members of powerless ethnic groups, and groups with strong baseline identity feelings or living in poorer areas, or areas with a history of conflict. Put together, these finding suggest a new dimension of the natural resource curse: the fragmentation of identities, between ethnic groups and nations.