This is a 10 cmlong unifacial convergent scraper from Gombore II made from Trachy-andesite, a volcanic rock, that was used in smaller quantities at different sites and chronological stages at Melka Kunture (for example at Gombore I, Garba, Melka-Garba).
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite, and ranges from 57 to 63% silicon dioxide (SiO2) .
Classification of andesite may be refined according to the most abundant phenocryst. For Example: hornblende-phyric andesite, if hornblende is the principal accessory mineral. At Melka Konture Trachy-andesite was used during the Acheulian and MSA. Trachy-andesiteis a mesocratic lava, lighter than the basalts, with generally numerous large phenocrystals of alkaline feldspaths.
The knowledge of the different volcanic episodes which occurred over the last several million years in the environment of the Melka Kunture prehistoric sites allows a new appraisal of the nature and abundance of emitted lavas that are represented in the alluviums of the Awash River and its tributaries. Moreover, the most compact facies can also be seen in the different archaeological sites. Several alluvial units and some archaeological layers have been sampled and petrographic counts performed on the basis of mainly macroscopic and some microscopic determinations of the lavas by recent research. They allow comparisons between samples and offer a better understanding of local available raw materials for use by hominins.
Melka Kunture lies in the upper Awash valley, 50 km south of Addis Ababa, at 2000m asl. The Awash basin extends for about 3000 km² at a height between 2500 and 2000 m a.s.l. It is delimited by several Pliocene volcanoes, the largest being the Wachacha and the Furi to the north, and the Boti and Agoïabi to the south. It is bordered to the east by the Ethiopian rift, part of the great rift system of eastern Africa. Fluvial sedimentation (pebbles, gravel, sand, and clay) was frequently interrupted by volcanic activity, whose products are important markers for stratigraphic correlations between the different archaeological sequences identified so far. Over 70 archaeological levels have been discovered so far, and more or less wide extensions of about 30 of them have been excavated.
The earliest at findings at Melka Kunture come from the Oldowan (at the sites Karre and at level B of Gombore I); with a K/Ar age near to 1,6/1,7 m.y. A probably contemporaneous Oldowan site has been investigated at Garba IV with a radiometrical age between 1-5 and 1,5 m.y. The reevaluation of the Garba IV site by Gallotti showed, that unit D of Garba IV is characterized by the emergence of a new chaîne opératoire focused on large flake/large cutting tool (LCT) production, and a large variability of small débitage modalities with systematic preparation of the striking platform and the appearance of a certain degree of predetermination , characteristic rather for an early Acheulian than for a Mode I industry-in good agreement with other early Acheulian dates in East Africa.
A later phase of the African Acheulean is well represented by several sites in the area of Gombore II (dated to about 0.8 Myr). The latest Acheulean site is Garba I, dated to ca. 0.5 Myr, while the end of this long sequence is represented, at Melka Kunture, by the site of Garba III, where there are also Middle Stone Age layers.
The East African Late Stone Age is poorly documented at Melka Kunture, being found so far at Wofi and Kella. A little less than 7 km from Melka Kunture, at Balchit, obsidian outcrops. As evidenced by the analyses of samples from several sites, this volcanic glass was an important raw material, frequently used ever since the Oldowan. The exploitation of obsidian in the Melka region went on until historical times, leaving in the area of Balchit extensive accumulations of tens of thousands of blades, cores, and residues.