Provenancing of obsidian artefacts has become an increasingly common practice in Near Eastern archaeology. However, knowledge of the geological sources of obsidian remains variable. The Group 3d source remains the prime example; it was identified as chemically distinct in the 1960s and can be recognised as eastern Anatolian but it still lacks a specific geological location and has remained a minor detail in most publications. This article draws attention to the previously underappreciated importance of the source in later prehistoric periods, profiling assemblages of Group 3d obsidian artefacts from Ubaid and Chalcolitihic Kenan Tepe and Halaf Domuztepe in south east Turkey, as well as more isolated artefacts from a further twelve sites. It reviews our knowledge of the chemical composition of Group 3d obsidian and its physical characteristics. The article also explores the spatial and chronological distribution of this type of obsidian, which had a particular significance from the 7th millennium cal. BC onwards.