Underneath the Cheshire towns of Northwich, Middlewich and Nantwich lies a layer of rock known as Northwich Halite. Halite is rock salt.
Since before Roman times, salty spring water had been used as a source of salt.
Today salt is mined in the area at Meadowbank, near Winsford. This is the UK’s largest rock salt mine and one of only three in the UK.
Machinery is used to dig the salt out from a depth of more than 150m. As the halite layer is removed, sections are left to support the rocks above so that the mine doesn’t collapse. This has resulted in over 260km of tunnels underneath the area between Winsford and Northwich.
The mine is accessed via three vertical shafts.
One is for the miners. Another is used to bring the salt to the surface. The third is used for machinery and ventilation, with huge fans at the bottom, sucking air down so that it can be circulated through the mine.
Machines are taken down the shaft in pieces and reassembled underground. These work continuously, digging out the salt and transferring it to a conveyor belt. It is then crushed and graded by size before being brought to the surface.
The main use for rock salt is gritting our roads in winter. The salt is stockpiled on the surface so that it is ready to go out, keeping the gritters supplied throughout the icy weather.
The salt has a pink tinge due to sand mixed up within it. Colours range from clear to pink to dark brown depending on the other rocks present with the halite.
You can find out loads more about rock salt mining, including pictures and videos, from the Compass Minerals website.
If you live near a hill you will probably find one of these on the roadside. Take a look at the halite inside.