The earliest record of rocksalt mining was in 1682 at Marbury near Northwich, and for the following 200 years the Northwich district dominated the rocksalt trade in Cheshire. The loss of overseas markets, and hence over-production in Cheshire caused a chaotic market and gradual decline in the rocksalt industry at the end of the 19th Century. In 1888, Salt Union was formed as a conglomerate of some 66 salt operators to endeavour to bring some order to the markets, but the use of poor mining practices (and subsequent catastrophic collapses) in Northwich was the main cause of the ultimate demise of the industry in that area.
In order to maximise the profits from sale of the salt, the mines were not designed for long-term stability, with only a minimum number of narrow pillars left in place for support, and therefore generally had a life expectancy of some 30 to 40 years. As the rocksalt is highly soluble, and natural groundwater occurred above the mine level, it was extremely difficult to maintain the integrity of the access shafts to the mines and abandonment was generally brought about by flooding, erosion and collapse of the shafts. Once freshwater had entered the mine via a compromised shaft, maintenance of pillar integrity became virtually impossible and pillars often failed following the failure of the shafts. In 1928 the Adelaide Mine in Marston was hastily evacuated due to flooding and this marked the end of rocksalt mining in Northwich.
The original access shafts for the currently operational Meadow Bank Rocksalt Mine at Winsford were sunk in 1844, but the mine was abandoned in working order in 1892 with the loss of rocksalt markets. The mine was reopened by Salt Union shortly after the closure of the Adelaide Mine in Northwich in 1928. With the gradual increase in demand for rocksalt, sales revenues eventually funded a full modernisation programme in 1960 which greatly enhanced the production capacity. The output in 1968 topped 1 million tonnes and comprised the whole of rocksalt production in Great Britain at that time. In 2014 Meadowbank celebrated its 170th anniversary and is Britain’s oldest working mine. Compass Minerals, who own and operate the mine, have been able to diversify their commercial operations utilising the void space in the areas of the mine previously worked; this includes a file storage business, of which the Board is a customer.