The Oyu Tolgoi mine Mongolian Оюу Толгой also Oyu Tolgoi Turquoise Hill is a combined open pit and underground mining project in Khanbogd sum within the south Gobi Desert approximately 235 kilometres 146 mi east of the 214 mn 246 govi Province capital Dalanzadgad The site was discovered in 2001 and is being developed as a joint