Where Does Magnesium Come From? The Rocks, the Sea, and a Lot of Processing
The magnesium in your evening glass is older than anything that has ever used it. It came out of rock or out of the sea, and turning it into something your body can absorb took a furnace.
I went looking for how that actually happens, partly because I stock the stuff and partly because I keep finding that knowing where a thing comes from changes how I use it.
Route 1: Out of the rock
The main ore is magnesite — magnesium carbonate — pulled from open-pit mines, with China supplying most of the world's output alongside Russia, Turkey, Austria and Brazil. Dolomite gets quarried in enormous quantities for the same purpose, and other magnesium minerals turn up as byproducts of potash mining.
None of it is usable as it comes. You have to calcine the ore, which means heating it hot enough to drive the carbon dioxide out of the carbonate and leave magnesium oxide behind. That step is where the energy goes, and it releases carbon twice — once from burning fuel to reach the temperature, and once from the rock itself coming apart.
Route 2: Out of the sea
The other route starts wet.
Magnesium is the third most abundant dissolved element in seawater, sitting at around thirteen hundred parts per million — which means every ocean on earth is a dilute magnesium solution. Add lime to seawater and magnesium hydroxide falls out as a solid. That's essentially the process the Dow Chemical Company ran during the Second World War, pulling magnesium out of the Gulf of Mexico.
The concentrated version uses brines rather than open ocean: the Dead Sea, the Great Salt Lake, Qinghai in western China, the Atacama in Chile. Sun and wind evaporate the water down in vast shallow ponds until what remains is rich enough to work with. In most of those places, magnesium comes up as a co-product alongside potash and lithium.
The thing that surprised me
Follow either route far enough and you arrive at magnesium oxide.
And magnesium oxide is where nearly every premium form begins. You take the oxide and react it with glycine to make magnesium glycinate. React it with citric acid and you get citrate. With lactic acid, lactate. The expensive, gentle, well-absorbed forms on the shelf are the cheap form, chemically converted.
That isn't a swindle, and I want to be clear about why. Binding magnesium to an amino acid genuinely changes how your gut handles it — glycinate is absorbed far better than oxide and is much easier on the digestion. The chelation is real chemistry doing real work.
But it does explain something about the price gap. You aren't paying for a rarer mineral. You're paying for a further step, and it's worth knowing the difference between those two things.
Route 3: The one grown by algae
There's a third route, and it's in the magnesium we carry.
Aquamin comes from Lithothamnion, a red coralline algae that spends its life pulling minerals out of seawater and laying them down in a calcified skeleton. Harvested from seabed deposits off Iceland and Ireland, it arrives carrying magnesium alongside the trace minerals the algae accumulated while it was alive. That's where the "plus seventy minerals" language comes from, and it's an accurate description of what the material is.
It's also the ingredient I'd most want documentation on. Those seabeds grow slowly — some of these deposits accumulated over thousands of years — and living beds of this algae are protected habitat in European waters for exactly that reason. Licensed operations harvest loose accumulated material rather than living growth, and a supplier will have the paperwork. Asking for it is the difference between a sustainability claim and a sustainability fact.
Epsom, 1618
In the summer of that year, a cowherd in Surrey noticed his cattle refusing to drink from a particular spring.
The water was bitter with dissolved magnesium sulfate. Word travelled, people came to drink it and bathe in it, and a small English town became a spa. The salts took the town's name and have kept it for four hundred years — long before anyone could have told you what magnesium does in a muscle, women were putting it in their bathwater and finding it good.
That thread never really went quiet. It just stopped being explained.
What the bath is actually doing
I have used Epsom salts for years on an assumption: that it would raise those levels body wide. A magnesium ion carries an electrical charge and travels wrapped in a shell of water molecules, and your skin barrier is extremely good at turning back exactly that kind of thing. The research on whether soaking meaningfully raises magnesium in the body is thin and unconvincing.
The bath is still worth taking. Heat relaxes muscle directly, buoyancy takes weight off joints, and an hour where nobody can reach you does something no mineral accounts for. Keep the ritual — it earns its place on its own terms.
The magnesium, though, is mostly staying in the water.
Which is why you swallow it
If you want magnesium reaching the muscle that won't let go of your shoulder, or the nervous system still running the day's argument at eleven at night, it has to go in through your mouth.
The magnesium we carry uses glycinate alongside two other well-absorbed forms, at three hundred milligrams of elemental magnesium in a single scoop. Stir it into something warm an hour before bed and drink it sitting down. Give it a couple of weeks — muscle and nervous system settling accumulate rather than arrive.
Then run the bath anyway. It was never really about the salts.
A note on limits: magnesium interacts with certain medications, including some antibiotics and thyroid medications, and anyone with kidney disease should not supplement it without medical supervision. Sleeplessness, anxiety, or muscle pain that persists deserves a provider rather than a powder.
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Frequently asked
Where does supplement magnesium actually come from?
Is one source of magnesium better than another?
References
- Magnesium — Fact Sheet for Health Professionals— NIH Office of Dietary Supplements
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