Why is armed civil conflict more common in resource-dependent countries than in others? Several studies have attempted to unravel mechanisms on why natural resources are linked to armed conflict, but no coherent picture has yet emerged. This article seeks to address this puzzle by concentrating on the issue of how rebel access to natural resources affects conflict. It uses data on gemstone and hydrocarbon localities throughout the world and controls for the spatial and temporal overlap of resources and conflict. The results show that the location of resources is crucial to their impact on conflict duration. If resources are located inside the actual conflict zone, the duration of conflict is doubled. Interestingly, oil and gas reserves have this effect on duration regardless of whether there has been production or not. In addition, a country-level analysis suggests that oil production increases the risk of conflict onset when located onshore; offshore production has no effect on onset. These results support the assertion that natural resources play a central role in armed civil conflicts because of the incentives and opportunities they present for rebel groups.