How magnesium metal is made
Most magnesium metal is baked out of dolomite rock in vacuum-sealed steel tubes.
- stations
- 5
- things upstream
- 7
- raw sources
- 4
- steps from the ground
- 3
The short version
Magnesium rarely occurs as a metal, so it is smelted from rock. In the Pidgeon process, dolomite is fired into magnesium oxide, mixed with ferrosilicon and heated in a vacuum until magnesium vapor condenses as crystals. Electrolysis of magnesium chloride, often from brine or seawater, is the other main route.
-
Fire the dolomite
Dolomite is calcined to drive off carbon dioxide. What remains is a mixed oxide of magnesium and calcium.
Goes in -
Blend in the reducing agent
The calcined rock is mixed with ferrosilicon, which strips the oxygen from the magnesium. Ferrosilicon is used in place of pure silicon because it is cheaper.
75% ferrosilicon
Goes in -
Heat it in a vacuum tank
The mixture is heated from outside in a sealed reduction tank under vacuum. Magnesium comes off as a vapor, while the calcium ends up as calcium silicate.
-
Collect the crystals
The vapor condenses on a cooler part of the tank as crystals, which crews pull out once the tank is opened.
-
Remelt into ingots
The crystals are remelted and cast into ingots, which go to alloy makers and die casters.
Worth repeating
- Magnesium is the second-most-abundant cation in seawater, so the ocean is a workable ore for plants that use electrolysis.
- The United States supplied 45 percent of world magnesium as recently as 1995, and only 7 percent by 2013 as China took over.
- Magnesium ranks eighth in abundance among elements in Earth's crust.
Back to the ground
Follow every input upstream and magnesium starts as these 4 raw sources.
Where it comes from
World production in 2017, per Wikipedia.
Where it goes next
Magnesium feeds 5 lines directly and reaches 162 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How magnesium metal is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/magnesium