river, rising in the southern outliers of the Fouta Djallon mountains of Guinea, northeast of Mamou. It flows 250 miles (400 km) north-northeast and east, past Dabola and Bissikrima, across grassy plains and savannas of stunted trees, to enter the Niger River just south of Siguiri. Alluvial gold deposits have long been worked along the Tinkisso River.