Obsidian aritfacts from the Melka-Konture site about 50 km south of Addis Ababa span the period from Oldowan to Late Stone age. A number of specimens from different levels have been examined petrographically and for their chemical compositions. All prove to be alkali rhyolite obsidians of virtually identical composition and petrographic character, differing only in degree of devitrification and hydration. They belong to Group lg of Renfrew <i>et al. (1966) and it is almost certain that their source is the nearby obsidian quarry at Baltchit. This seems to have been opened in a short flow which appears to be unrelated to the large extinct recent volcano, Wachacha, which lies to the northwest. -- AATA