What Is Rock Salt?
Rock salt, also known as halite, is the natural mineral form of sodium chloride (NaCl). It has been used for thousands of years for preservation, trade and industry. In the UK, many towns ending in “wich” or “wick” reflect historic salt production.

Today, rock salt is most commonly used as road salt for winter gritting and de-icing.

How Was UK Rock Salt Formed?
UK rock salt deposits were formed around 220 million years ago during the Triassic period. At that time, shallow inland seas repeatedly evaporated, leaving behind thick salt layers beneath the surface.

These ancient salt beds now supply the majority of the UK’s winter road salt.

Where Does UK Road Salt Come From?
The UK has three active indigenous rock salt mines. The largest mainland mine is located in Winsford, producing around one million tonnes of salt per year.

Depending on winter severity, between 750,000 and 2 million tonnes of salt are used annually to grit UK roads.

How Is Rock Salt Mined?
Rock salt is extracted using a method called room and pillar mining. Large chambers are cut into the salt deposit, while pillars of salt are left in place to support the roof.

The salt is:

  • Crushed and screened underground
  • Transported to the surface via conveyor systems
  • Treated with an anti-caking agent to keep it dry and free-flowing
  • This ensures it spreads evenly during winter gritting.

Why Is UK Road Salt Brown?
UK road salt is typically brown due to natural impurities such as clay, sand and other minerals mixed with the sodium chloride during formation.

These minerals can improve traction on icy roads, although they may leave some residue after winter.

How Does Road Salt Melt Ice?
Road salt works by lowering the freezing point of water — a process called freezing point depression.

When salt contacts ice:

  1. It dissolves in the thin layer of water on the surface
  2. Forms a brine solution
  3. Prevents ice from bonding to the road
  4. This makes it easier for traffic and snow ploughs to clear surfaces effectively.