What is the natural source of magnesium chloride?

January 12, 2026 •

4 min read

Magnesium is the eighth most abundant element in the Earth's crust, yet it is rarely found in its pure state due to its high reactivity. Instead, it combines with other elements to form compounds, with magnesium chloride being one of its most common and versatile forms. It is highly soluble in water, which is why its primary natural sources are found in saline aquatic environments and mineral deposits left behind by evaporated water.

Quick Summary

The natural sources of magnesium chloride include vast bodies of saline water like the oceans and the Dead Sea, as well as mineral deposits and underground brine reserves. Evaporation from ancient seas created mineral beds rich in bischofite and carnallite, from which magnesium chloride is extracted.

Key Points

Ancient Evaporite Deposits: Mineral beds from ancient seas, like the Zechstein seabed, contain concentrated bischofite (MgCl2·6H2O), a key natural source.
Saline Water Bodies: Oceans, the Dead Sea, and the Great Salt Lake are rich with dissolved magnesium chloride, forming a major and accessible natural resource.
Carnallite Mineral: Found in marine salt deposits, this hydrated double salt (KMgCl3·6H2O) is a natural source mined for both potassium and magnesium.
Brine Extraction: Magnesium chloride is extracted from modern brines through processes that involve solar evaporation or chemical precipitation, like the Dow Process.
Continuous Supply: While mineral deposits are finite, the vast and renewable nature of seawater and saline lakes ensures an enduring natural supply.
Industrial Significance: The naturally sourced compound is critical for a variety of products, including pharmaceuticals, food additives, and industrial chemicals.

Ancient Mineral Deposits

Long before modern times, the Earth's oceans underwent significant geological changes, including periods of intense evaporation. As these ancient seas dried up, they left behind massive, concentrated salt deposits known as evaporites. These mineral beds are now buried deep underground and are one of the most significant sources of natural magnesium chloride.

Bischofite

One of the most important mineral forms of hydrated magnesium chloride is bischofite, with the chemical formula MgCl2·6H2O. This colorless, crystalline salt is extracted from ancient seabeds, such as the Zechstein seabed in northwest Europe, through a process called solution mining. Here's how this process generally works:

Water is pumped into the underground deposit to dissolve the bischofite and other soluble salts.
The resulting brine is then pumped back to the surface.
The brine is treated and purified to separate the magnesium chloride from other minerals.

Carnallite

Another crucial mineral source is carnallite, a hydrated double salt with the formula KMgCl3·6H2O. Carnallite is a key source of both potassium and magnesium, forming alongside other chlorides in marine evaporite deposits. The mineral is mined from deposits found in locations like Stassfurt, Germany, and the Perm Basin in Russia. From there, the carnallite ore is processed to separate the potassium and magnesium components.

Seawater and Salt Lakes

Beyond ancient deposits, modern saline bodies of water are a continuous and abundant source of magnesium chloride. The oceans of the world, though only containing about 0.13 percent magnesium by weight, are an almost inexhaustible supply. Salt lakes and concentrated brines offer an even higher ratio of magnesium chloride.

The Dow Process

This is a major industrial method for extracting magnesium from seawater. It involves a chemical precipitation process followed by conversion and electrolysis.

Precipitation: Seawater is treated with slaked lime, causing magnesium hydroxide to precipitate as a solid.
Conversion: The magnesium hydroxide is reacted with hydrochloric acid to produce magnesium chloride.
Refining: The resulting magnesium chloride brine is then refined to remove impurities and concentrated for further use.

The Dead Sea

The Dead Sea, located in the Jordan Valley, is famous for its exceptionally high salt concentration, making it a rich source of magnesium chloride. The mineral content of the Dead Sea can be as high as 50.8% magnesium chloride. Extraction from the Dead Sea involves a process of solar evaporation and crystallization.

Great Salt Lake Brine

In North America, brines from the Great Salt Lake are a significant source of magnesium chloride. Like the Dead Sea, the lake's concentrated mineral content allows for efficient extraction and processing of the valuable compound.

Comparison of Natural Magnesium Chloride Sources


Feature	Ancient Mineral Deposits	Seawater & Salt Lakes
Source Type	Solid mineral formations (e.g., bischofite, carnallite) left by evaporated ancient seas.	Dissolved salts in modern, highly saline bodies of water (e.g., oceans, Dead Sea, Great Salt Lake).
Extraction Method	Solution mining (pumping water in and brine out) or traditional mining for ore.	Evaporation ponds (solar) or chemical precipitation (Dow Process).
Purity	Can be highly concentrated in specific minerals, but may require extensive processing to remove other salts.	The Dow Process allows for high purity, but the initial brine contains a mix of many minerals.
Dependability	Finite, but often large and reliable sources once located and secured.	Almost inexhaustible, but may be affected by environmental factors like pollution.
Byproducts	Processing often yields other salts, such as potassium chloride from carnallite.	Extraction from seawater can be integrated with other chemical manufacturing processes.

Global Impact of Magnesium Chloride Sources

Different regions of the world rely on their unique geological features for the production of magnesium chloride. For instance, the Zechstein Sea deposits have been crucial for European production for centuries, providing a high-purity source of bischofite. In contrast, countries with access to saline lakes, like the US with the Great Salt Lake, have developed industrial processes to extract the mineral from brine. The vastness of the Dead Sea makes it a powerhouse of magnesium production, with its unique chemistry providing a particularly rich source. These diverse natural sources ensure a steady global supply for industries ranging from medicine and food production to construction and de-icing.

Conclusion

Magnesium chloride is sourced naturally from several key locations around the world, most notably from mineral deposits formed by ancient evaporated seas and from the concentrated brines of modern saline lakes and oceans. The primary mineral is bischofite, found in underground beds, while seawater is a continuously renewable resource. Extraction methods vary depending on the source, utilizing either mining, solar evaporation, or chemical precipitation processes. These natural sources are critical for numerous industrial and consumer products, from magnesium supplements to road de-icing agents, underscoring the importance of understanding their origins and extraction processes.

Frequently Asked Questions

The most common and important mineral form is bischofite, which is hydrated magnesium chloride (MgCl2·6H2O). It is found in ancient evaporated seabed deposits.

Magnesium chloride is extracted from seawater through industrial processes like the Dow Process, where it is first precipitated as magnesium hydroxide and then reacted with hydrochloric acid to form magnesium chloride.

Yes, highly saline bodies of water like the Dead Sea and the Great Salt Lake are concentrated sources of magnesium chloride. It is extracted from their brines using evaporation and crystallization.

The Zechstein seabed is a famous ancient seabed in northwest Europe from which the mineral bischofite is extracted through solution mining.

Yes, carnallite is a hydrated double salt containing both magnesium and potassium chlorides, and is a natural source mined for both of these elements.

Ancient evaporite deposits form when seas or salt lakes dry up over geological time. The dissolved salts precipitate and form concentrated mineral beds that are then covered by other layers of rock.

The Dead Sea, with its exceptionally high magnesium chloride ratio, is a major source for extraction. Its brine is processed using solar evaporation to produce magnesium chloride.