Where Does Epsom Salt Come From?

The Rites of Salt Epsom Bath Salts with magnesium sulphate crystals and independent TTI laboratory report

Epsom salt is named after Epsom in Surrey, England, where a spring of bitter mineral water was found around 1618 — but the name stopped being a postcode a long time ago. Epsom salt is the common name for magnesium sulphate heptahydrate (MgSO₄·7H₂O), and commercial supplies are produced and traded internationally, typically from mined magnesium-sulphate minerals or by reacting magnesium compounds with sulphuric acid. As early as 1876, a guidebook to the area noted that none was made at Epsom. The word “Epsom” on a pack tells you what the substance is. It does not tell you where that pack came from — only the brand’s sourcing documents can.

Does Epsom salt actually come from Epsom?

Historically, yes. Today, Epsom salt generally does not come from Epsom. Epsom salt takes its name from mineral water discovered on Epsom Common in Surrey in the early 17th century. The traditional story — recorded in the 1600s and repeated in Victorian guidebooks — credits a local man, Henry Wicker, with finding water standing in a hoof-print during a dry summer around 1618. Details of the anecdote vary between accounts, so it is best treated as tradition rather than record. The well was enclosed by 1621, and Epsom grew into one of England’s fashionable spa towns.

The salt itself came later. In the 1690s, the physician and botanist Nehemiah Grew extracted the salt from Epsom’s spring water, published an analysis of it and sought a patent on its production — which led to a public dispute with apothecaries selling their own versions. Sources give slightly different years for Grew’s treatise (between 1693 and 1697), but they agree he was the person who isolated and described the salt.

By the 19th century, the connection with the town had become a name rather than a supply. James Thorne’s Handbook to the Environs of London (1876) recorded that Epsom salt was by then “manufactured on a large scale and at a very low price, but none is made at Epsom.” We found no evidence of commercial Epsom salt production in Epsom today.

What is Epsom salt made of?

Epsom salt is magnesium sulphate (also spelled magnesium sulfate) with water built into the crystal. The common form is magnesium sulphate heptahydrate, MgSO₄·7H₂O — each unit of magnesium sulphate bound to seven molecules of water.

Epsom salt is not sodium chloride, the compound in table salt. “Salt” here is used in the chemist’s sense: a compound of positive and negative ions — in this case, magnesium and sulphate. Epsom salt and table salt share a word, not a chemistry. The Science covers that difference in more depth.

Is Epsom salt natural or man-made?

Magnesium sulphate occurs naturally, but the Epsom salt sold in shops has been through industrial processing — and whether its starting point was a mined mineral or a chemical route depends on the producer. “Natural or man-made” is a neater split than reality allows, so it helps to separate the two ideas.

Where is Epsom salt found in nature?

The natural mineral form of Epsom salt is called epsomite — named after Epsom. According to the Handbook of Mineralogy, epsomite forms as crusts on the walls of mines and caves, through evaporation at mineral springs and salt lakes, and when another magnesium-sulphate mineral, kieserite (MgSO₄·H₂O), takes up water. Kieserite is common in evaporite salt deposits. The spring water at Epsom was one natural source among many, not the only one.

How is commercial Epsom salt made?

Reference data compiled in PubChem describes two broad routes for producing magnesium sulphate commercially:

  1. Recovering naturally occurring minerals such as kieserite or epsomite, then processing them.
  2. Reacting sulphuric acid with magnesium oxide, magnesium hydroxide or magnesium carbonate.

Either way, the uniform white crystals in a retail pack have been dissolved, purified, crystallised, dried or sized at some stage. Producers describe their own routes differently: the German producer K+S, for example, says it sources raw material for its magnesium sulphate from its own mines in Germany and refines it.

So a product labelled “natural Epsom salt” may well use a mined mineral as its raw material — but it will not have been dug out of the ground in the form you pour into a bath. The word “natural” on a pack does not tell you which production route was used. Only producer documentation can.

Where does the Epsom salt sold today come from?

Epsom salt sold in the UK today comes through international supply chains, and the name “Epsom” does not identify any country, mine or factory. Magnesium sulphate is an industrially produced and internationally traded material, and UK retail listings show different declared countries of origin for products sold as Epsom salt — one major UK pharmacy chain’s listing for a leading Epsom bath salt, for example, gives the country of origin as Germany.

On a modern pack, “Epsom” names a substance. It does not tell you where that bag was made.

A declared country of origin is useful, but limited. It names a country. On its own, it does not tell you which company produced the raw material, whether that material was mined or chemically produced, or whether the batch in your hand was independently tested.

Where does The Rites of Salt Epsom salt come from?

The Rites of Salt’s Epsom Bath Salts are supplied from China. We hold the supplier’s certificate of analysis for the magnesium sulphate, which identifies the material, crystal size and batch. That documentation establishes our supply chain. It does not establish whether the material was originally mined or chemically produced, so we don’t claim either.

What we can document separately is independent testing of the product we sell in the UK. TTI Testing Laboratories tested our Epsom Bath Salts (report Tti-05401-25) and measured 98.616% magnesium sulphate, with mercury not detected at the method’s detection limit of 0.1 mg/kg. You can read the result on our Lab Reports page.

Our Epsom salt is sold as a bath salt, for external use only, and has a Cosmetic Product Safety Report (CPSR) for that use. It is not sold for eating. For sizes, testing and the full product picture, see our Epsom Salts UK guide.

How can you tell where an Epsom salt product comes from?

Check the documents, not the name. Five things separate a genuine origin answer from a vague one:

  1. Country of origin on the pack. Under UK cosmetics labelling rules, imported cosmetic products must state their country of origin. It is a starting point — but it names a country, not a source or a production process.
  2. Supplier documentation. Can the brand show that it holds supplier paperwork for the magnesium sulphate — and does it say what that paperwork does and does not establish? “Responsibly sourced” on its own is not an answer.
  3. Batch information. A batch reference connects a document to a specific quantity of material. Without one, a certificate could describe anything.
  4. Independent testing of the finished product. Look for a named laboratory, a report number and actual results — ideally published. A supplier’s own certificate and a third-party test on the retail product are different things, and they answer different questions.
  5. Origin claims and testing claims are separate. Testing shows what a sample contains; it does not show where the material came from. Supply documents show where it came from; they do not show what is in the pack you bought. A confident answer needs both.

If you are choosing between products rather than researching origin, our guide to what to check before buying Epsom salt covers composition, testing and safety paperwork.

Frequently asked questions

Are Epsom salts from Epsom?

Epsom salts are named after Epsom in Surrey, where a magnesium-sulphate-rich spring was found around 1618. Epsom salt sold today is generally not produced in Epsom; as early as 1876, a guide to the area recorded that none was made there.

Is Epsom salt mined?

Some magnesium sulphate is produced from mined minerals such as kieserite; some is produced by reacting magnesium compounds with sulphuric acid. In both cases, retail Epsom salt is industrially processed before it is packed.

What is Epsom salt made of?

Epsom salt is magnesium sulphate heptahydrate, MgSO₄·7H₂O — magnesium sulphate with seven molecules of water bound into each crystal unit. It is not sodium chloride.

Where is Epsom salt found in nature?

Epsom salt’s natural mineral form, epsomite, forms as crusts in mines and caves, through evaporation at mineral springs and salt lakes, and when the mineral kieserite absorbs water.

The bottom line

Epsom salt comes from Epsom in name only. It was first identified in spring water on Epsom Common in Surrey in the 17th century; today, Epsom salt is magnesium sulphate produced and traded internationally, from mined minerals or chemical routes. To know where a particular Epsom salt comes from, ask the brand what its supply documentation shows — and what its independent testing shows. Ours are above.

Sources & further reading