Rob and Nan Lake is located 100 metres east of the Meadow Lake road and 18 kilometres west of 70 Mile House.
The lake is a semi-evaporitic playa lake. It is located in the "Green Timber Plateau" area (EMPR Bulletin 4), a semi-arid plateau area averaging 1130 metres elevation which is part of the Cariboo Plateau and host to several playa lakes. The area is underlain by alkaline plateau basalt flows of the Miocene to Pleistocene Chilcotin Group, mantled by a thin cover of glacial till and glaciofluvial sediments. Annual precipitation averages between 300 and 400 millimetres (EMPR Paper 1991-1).
Rob and Nan Lake covers approximately 10 hectares (EMPR Bulletin 4, page 13) which contains approximately 40 centimetres of sodium carbonate-rich brine. The specific gravity of the brine in 1937 was 1.065, containing 6.39 per cent total dissolved solids of the following composition: 86.5 per cent sodium carbonate, 6.5 per cent sodium sulphate and 7.5 per cent sodium chloride. There is no record of "winter crystal" having formed in the lake. Canadian Occidental Petroleum staked the Soda 6 and 7 claims in 1989, collected a water, a mud and a winter crystal sample and completed analyses for sodium carbonate and other alkalai salts (Assessment Report 20080). Canoxy also completed an airborne infrared survey to test for dissolved solids in the lakewaters. In 1993, the lake was re-staked as the CSW 2 and 3 claims by Mr. G.M. Rogers who collected five water samples to test for the presence of natron winter crystal. A trace was found.