How Large Are Overseas Silicon-Magnesium Reserves?
Outside China, identified silicon-magnesium ore reserves are estimated at roughly 2.5 billion tonnes. That tonnage is spread across Australia, Brazil, Canada, South Africa, Indonesia and a number of smaller producing countries. Because magnesium-bearing silicates and their host rocks are bulky, low-value materials, the commercial strength of a reserve base depends far more on ore grade, strip ratio, energy availability and distance to a bulk port than on the headline figure alone.
The table below summarises the reserve figures most often quoted for the five leading overseas sources, together with their main mining regions and their role in the magnesium ferrosilicon supply chain.
| Country | Estimated reserves (million t) | Main regions | Role in supply |
|---|---|---|---|
| Australia | 500 | Western Australia | Large-scale ore and alloy feedstock |
| Brazil | 400 | Minas Gerais, Sao Paulo | Domestic and export alloy supply |
| Canada | 250 | Ontario, Quebec | Mature mining and processing base |
| South Africa | 200 | Northern Cape, Mpumalanga | Leading African producer |
| Indonesia | 150 | Java, Sumatra, Kalimantan | Fast-growing regional source |
Country-by-Country Reserve Profile
Australia holds an estimated 500 million tonnes, most of it in Western Australia, and its output has long ranked among the highest in the world. Brazil accounts for about 400 million tonnes in Minas Gerais and Sao Paulo, close to established industrial corridors and ports. Canada reports some 250 million tonnes in Ontario and Quebec, backed by mature mining, reliable grid power and experienced metallurgical engineering. South Africa holds about 200 million tonnes in the Northern Cape and Mpumalanga, the largest identified base in Africa. Indonesia has around 150 million tonnes across Java, Sumatra and Kalimantan and keeps expanding its regional position.
From Ore Reserves to FeSiMg Master Alloy
Reserve tonnage only becomes useful to a foundry once it is converted into a controlled master alloy. Magnesium ferrosilicon, normally written FeSiMg, is the standard spheroidizing agent for ductile iron: feedstock is smelted, alloyed with silicon and magnesium, and usually modified with rare earth elements so that the nodularising reaction stays predictable at the ladle. Two conclusions follow. Overseas raw material is abundant, so supply shocks usually come from energy, freight or trade policy rather than geological scarcity; and magnesium and rare earth contents, not ore tonnage, decide the value a foundry actually receives.
Typical Rare Earth FeSiMg Nodulizer Grades
Magnesium rises from 5.5% to 9.0% and rare earth from 0.5% to 7.5%, silicon is held in the 40-46% band, calcium sits at 2.0-3.5%, barium is matched to the treatment practice, aluminium is kept below 0.8% and iron forms the balance.
| Grade | Code | Mg (%) | Re (%) | Si (%) | Ca (%) | Al max (%) | Fe |
|---|---|---|---|---|---|---|---|
| FeSiMg5RE1 | 5-1 | 5.5-6.5 | 0.5-1.5 | 40-46 | 2.0-3.5 | <0.8 | Balance |
| FeSiMg5RE2 | 5-2 | 5.5-6.5 | 1.5-2.5 | 40-46 | 2.0-3.5 | <0.8 | Balance |
| FeSiMg6RE2 | 6-2 | 6.0-7.0 | 1.5-2.5 | 40-46 | 2.0-3.5 | <0.8 | Balance |
| FeSiMg7RE2 | 7-2 | 6.5-7.5 | 1.5-2.5 | 40-46 | 2.0-3.5 | <0.8 | Balance |
| FeSiMg7RE3 | 7-3 | 6.5-7.5 | 2.5-3.5 | 40-46 | 2.0-3.5 | <0.8 | Balance |
| FeSiMg8RE3 | 8-3 | 7.5-8.5 | 2.5-3.5 | 40-46 | 2.0-3.5 | <0.8 | Balance |
| FeSiMg8RE5 | 8-5 | 7.5-8.5 | 4.5-5.5 | 40-46 | 2.0-3.5 | <0.8 | Balance |
| FeSiMg8RE7 | 8-7 | 7.0-9.0 | 6.5-7.5 | 40-46 | 2.0-4.0 | <0.8 | Balance |
Lower grades such as 5-1 and 5-2 suit open ladle and sandwich treatment of moderate-sulphur iron; grades from 7-3 to 8-7 suit heavier sections, higher sulphur melts and where fade resistance is critical.
What to Check Before Placing an Order
Magnesium and rare earth ranges against treatment method, section thickness and sulphur level of the melt.
Silicon content, which affects both magnesium recovery and the alloy addition rate.
Calcium, barium and aluminium limits, because these change slag behaviour and inclusion risk.
Particle size distribution, commonly 5-25 mm for ladle work, with fines kept low.
Chemical consistency from lot to lot and the sampling method used at the works.
Frequently Asked Questions
Q: How much silicon-magnesium ore is available outside China?
Identified overseas reserves are estimated at about 2.5 billion tonnes, spread mainly across Australia, Brazil, Canada, South Africa and Indonesia.
Q: Which country has the largest overseas reserve?
Australia leads with roughly 500 million tonnes, largely in Western Australia, followed by Brazil with about 400 million tonnes.
Q: Does reserve size decide the price of FeSiMg?
Only indirectly. Alloy prices are set by magnesium and rare earth content, energy and freight costs, and conversion capacity rather than by ore tonnage.
Q: What does the number in FeSiMg8RE5 mean?
The first figure is the nominal magnesium content of 8% and the second is the nominal rare earth content of 5%; the letters mark the FeSiMg family.
Q: Is a higher magnesium grade always better?
No. Grades above what the treatment method can absorb increase reaction violence, slag and magnesium loss, so the grade should match the process.