What is Rock Salt

How is Rock Salt different from Sea Salt?

The Importance of Salt

Salt is vital to human life, and there are 250 grams of salt in the human body. There is so much salt in the world's oceans that there is enough to cover Britain in a layer of salt fifty miles deep.

It has been used in religious ceremonies to symbolise purity and was used by the Egyptians for preserving mummies. Roman soldiers were sometimes paid in salt.

What is Rock Salt?

Rock salt, known as halite, is a rock composed mainly of sodium chloride with additional trace elements. Wherever it is found in the world, it was formed by the evaporation of lake or ocean water.

This happens when a body of water is cut off without a source of replenishment from rain or rivers. A good example of this is the Dead Sea, whose single river, the Jordan, is dwindling through a drought.

The Dead Sea is drying up, and rock salt deposits are forming as the salt settles as crystals on the seabed.

Several towns in Cheshire, which in the nineteenth century produced 87% of Britain's salt, have names ending in wich, meaning a salty stream. People used these as a source of salt, but later dug mines and discovered vast salt deposits.

These salt deposits were laid down when an arm of an ancient ocean was cut off from the sea in a land surrounded by desert. Without rain, the water dried up, leaving its salt behind.

As Britain was then at the equator, the high temperatures added to lack of rain, so the evaporation was total.

Later sediments overlaid these salt deposits, but as salt was lighter than they were, it moved upwards into salt domes within the later deposits, bringing them nearer to the surface and making them easier to mine.

Rock salt is brown from the minerals in it. It is often used for industrial purposes, such as gritting roads and in over 14000 products ranging from foodstuffs to chemicals.

Mining Rock Salt

Let's take Cheshire as an example. The salt mines reach 100 metres deep and consist of a network of tunnels 140 miles in length, as far as it is from London to Brussels.

The salt is cut by huge machines with rotating cutting heads made of tungsten carbide, a hard substance often used in cutting tools. The fragments are taken to underground crushing plants.

Most of the machines are assembled underground by engineers and spend their working lives down the mine. To prevent the mine roof from caving in great pillars of salt are left as roof supports.

The salt is treated with a caking agent after extraction, making it easier to handle.

Sea Salt

White sea salt is made by evaporating seawater. This process is less expensive in sunnier countries, so much of it is imported to Britain, but there are local brands, including one that comes from the clean waters near Anglesey.

White marine salt leaves less deposit than brown rock salt and is used for cooking and for places where owners want the rock salt deposit not to be trodden into carpets etc.

We offer rock salt spreading throughout Aberdeen, Peterhead, Dundee and Aberdeenshire. Follow the link below to find out more about the areas that we offer road gritting in north Scotland.