Buildings at the gypsum factory operated by the Waratah Gypsum Company at Stenhouse Bay.

The rock gypsum mined at Inneston and Stenhouse Bay was washed and then processed to produce plaster of paris and chalk. The kettle process was used and in 1921 the factory had a capacity of 300 tons of plaster a week. At that time too there were plans to increase production with the installation of another kettle, and a rotary dryer and pre-heater which would also increase production. The steam engine was powered by mallee roots and wood. Careful regulation of temperature and time was required 'to maintain uniformity in the rate of setting of the finished product' (Jack, p. 92).

Gypsum is used in the production of cement, as a fertiliser or soil stimulant and for the manufacture of plaster of paris for the building trade. Rock gypsum and flour gypsum (or caso or kopi) were commonly mined at Inneston and Stenhouse Bay.

Writing in 1921 Jack, the Deputy Government Geologist, estimated that there were between 4.5 and 5.5 million tons of recoverable gypsum in the area (Jack, p. 106).

Nelson, Keith Kitchener The history of Marion Bay, Inneston and Stenhouse Bay, 1922-1939 [Warooka, S. Aust.: Warooka District Council], c1994

Gypsum in South Australia Adelaide, S. Aust.: Dept. of Mines, [1966]

Jack, R. Lockhart The salt and gypsum resources of South Australia Adelaide: Dept. of Mines; 1921