A basin, about 2.7 kilometres wide, contains a 50 metre thick layer of salt and mud below a 30 metre thick layer of clay. The basin is bounded to the west by quartz diorite and to the east by biotite-garnet-sillimanite-hornblende gneiss. Analysis of a dry sample gave 98.15 per cent sodium chloride and 1.82 per cent calcium sulphate (Minister of Mines Annual Report 1913).