gems, corundum, Ethiopia.12, sapphire, Chila, Tigray, locality, species

Following the discovery of sapphires in the Chila area of Tigray Province in late 2016, mining and trading activities in northern Ethiopia have become increasingly active. In collaboration with Ethiopia’s Ministry of Mines, the author visited sapphire mines and markets in the Tigray region for one week from late May to early June 2017. Sapphire mining was underway in the area surrounding Chila, which also serves as a trading hub. The deposits are all alluvial and extend northward from Aksum toward the Eritrean border. The initial discovery was near Chila (14°16’23.94”N, 38°38’4.26”E), with additional mining areas identified west-northwest of Chila (14°19’58.48”N, 38°36’4.86”E), east toward Rama, and west of Chila. In June 2017, higher-quality sapphires were found southeast of Chila near Aksum University. According to a 1999 geological map by the Geological Survey of Ethiopia, the sapphire-bearing region is predominantly underlain by Neoproterozoic basement rocks, with southern areas covered by Paleozoic to Mesozoic sediments and Tertiary volcanic rocks, especially around Aksum and locally near Chila. These Tertiary units include stratified basaltic rocks of the Koyetsa Volcanics, as well as the Adwa Trachyte and Phonolite, which now appear as isolated hills—remnants of broader eruptions later eroded. Given the magmatic characteristics of the sapphires, it is likely that the alluvial deposits resulted from the weathering of these Tertiary volcanic rocks. Geochemically, some of these volcanic units correlate with suites in central and southeastern Eritrea.