Borneo's South Kalimantan alluvial Cempaka Diamond Mines are located along rivers from Riam Kanan lake and the Barito, Murung, and Negara rivers, flowing from the Pegunungan Meratus mountain range. Indigenous artisanal miners from the Lukaas and Sungai Tiung villages in Tengah Province work the hand-dug river-bank gravel pits.