Valuable and versatile - salt has been important to manufacturing for centuries.
Exploitation of wild salt springs pre-dates Roman occupation of the UK, though the emphasis shifted over the last two millennia to mining.
While halite is excavated from the ground, as grit salt to de-ice roads in winter and for a host of other uses, the significance and historical impact of the most ancient of these mines is being preserved.
Used for tanning leather, manufacturing, food preservation, medication and even as currency that replaced metal coins, salt remains as useful now as it has ever been.
A single massive bed of salt stretches from Eire to the UK to mainland Europe, providing grit salt for roads as well as rock salt (halite) for manufacturing - such as tanning - and the food industry - for example, in preservation.
These salt deposits, which have been mined for hundreds of years in some cases, were laid down in the Triassic period, around 220 million years ago.
This, and the locations of present day inland rock salt mines, reveals that all these areas were once under water.
While this salt bed is one continuous expanse, spreading thousands of miles, the colour and even consistency of the grit salt within it is quite variable.
For example, desert sand will tint the normally clear grit salt pink or brown, while other geological influences will turn it blue or even green.
In Winsford, Cheshire, the ancient salt seam was laid down with alternating layers of Keuper Marl rock and the rock salt has a pink tint to it.
Keuper Marl - now officially known as the Mercia Mudstone Group - are strata of dolostone, shales or claystones and evaporates.
Winsford Rock Salt Mine has four layers of salt in all, although only two are being mined as they are considered the most economically viable and productive.
These 25-metre thick layers, 220 metres below the Earth's surface, have been subjected to pressure from the movement of tectonic plates over the millions of years since they were laid, and are twisted and broken by faults and folds.
Across Europe, the now non-operational Wieliczka Salt Mine in Poland is one of the oldest surviving grit salt mine in the world.
Established before 1290, though its actual origins are lost in time, Wieliczka excavated 26 surface shafts and 180 smaller shafts, extending from the upper-most salt bed only 57 metres below the surface, to 327 metres underground.
Wieliczka is now a protected historical monument with around 2,350 chambers and more than 240 km of galleries carved into the grit salt deposits.
Among them is the Holy Cross Chapel, which dates back to a potentially catastrophic event in the mid-19th century that threatened the lives of miners.
The mine is a tourist attraction, unlike the mine at Winsford, which is still working and produces around one million tonnes of rock salt and grit salt a year.
Exploitation of wild salt springs pre-dates Roman occupation of the UK, though the emphasis shifted over the last two millennia to mining.
While halite is excavated from the ground, as grit salt to de-ice roads in winter and for a host of other uses, the significance and historical impact of the most ancient of these mines is being preserved.
Used for tanning leather, manufacturing, food preservation, medication and even as currency that replaced metal coins, salt remains as useful now as it has ever been.
A single massive bed of salt stretches from Eire to the UK to mainland Europe, providing grit salt for roads as well as rock salt (halite) for manufacturing - such as tanning - and the food industry - for example, in preservation.
These salt deposits, which have been mined for hundreds of years in some cases, were laid down in the Triassic period, around 220 million years ago.
This, and the locations of present day inland rock salt mines, reveals that all these areas were once under water.
While this salt bed is one continuous expanse, spreading thousands of miles, the colour and even consistency of the grit salt within it is quite variable.
For example, desert sand will tint the normally clear grit salt pink or brown, while other geological influences will turn it blue or even green.
In Winsford, Cheshire, the ancient salt seam was laid down with alternating layers of Keuper Marl rock and the rock salt has a pink tint to it.
Keuper Marl - now officially known as the Mercia Mudstone Group - are strata of dolostone, shales or claystones and evaporates.
Winsford Rock Salt Mine has four layers of salt in all, although only two are being mined as they are considered the most economically viable and productive.
These 25-metre thick layers, 220 metres below the Earth's surface, have been subjected to pressure from the movement of tectonic plates over the millions of years since they were laid, and are twisted and broken by faults and folds.
Across Europe, the now non-operational Wieliczka Salt Mine in Poland is one of the oldest surviving grit salt mine in the world.
Established before 1290, though its actual origins are lost in time, Wieliczka excavated 26 surface shafts and 180 smaller shafts, extending from the upper-most salt bed only 57 metres below the surface, to 327 metres underground.
Wieliczka is now a protected historical monument with around 2,350 chambers and more than 240 km of galleries carved into the grit salt deposits.
Among them is the Holy Cross Chapel, which dates back to a potentially catastrophic event in the mid-19th century that threatened the lives of miners.
The mine is a tourist attraction, unlike the mine at Winsford, which is still working and produces around one million tonnes of rock salt and grit salt a year.