Guide
Is Feldspar Magnetic? Why It Needs Iron Removal and How It Is Done
Short answer: feldspar is not the problem, the iron-bearing minerals that come with it are. They are only weakly magnetic, which is why feldspar iron removal needs a high-intensity field.
The short answer
Feldspar is a ceramic and glass raw material, and higher-grade glass and ceramic products need low-iron feldspar. Many deposits have high iron content. The iron sits in iron minerals, biotite, amphibole and tourmaline, which are only weakly magnetic, so a strong (high-intensity) magnetic field is needed to separate them. In a Quang Nam quartz–feldspar ore study the iron sat in iron-mineral coatings on muscovite and as inclusions in the feldspar.
How much iron is too much
- Raw feldspar from Quang Nam, Vietnam measured 0.51–1.00% Fe₂O₃ (average 0.75%).
- Vietnamese standard TCVN 6598:2000 allows at most 0.3% Fe₂O₃ for feldspar used in ceramic glazes and at most 0.5% for ceramic bodies.
- Two raw-ore powders assayed by a third-party lab showed Fe₂O₃ of 0.24% (M1NES1) and 0.25% (M1NES2). These are feed compositions only, not iron-removal results.
Many raw feldspars therefore need iron removal before they can be sold as glaze grade.
What a magnet can and cannot remove
| Iron form | Magnetic response | Stage |
|---|---|---|
| Strongly magnetic material, liberated magnetite | Strong | Permanent magnetic separator first |
| Biotite, amphibole, tourmaline, iron oxides, iron worn off equipment | Weak | Electromagnetic high-gradient separator |
| Iron inside the mineral structure, or coated on mica | Not fully removed | May need flotation or chemical bleaching |
Where the iron is in free iron oxides, biotite or iron worn off equipment, wet high-gradient separation typically lowers Fe₂O₃ by about 30–70% in feldspar, with a whiteness gain of a few points. These are ore-dependent ranges, not guarantees; a sample test gives the real figure.
Wet or dry feldspar line
Wet processing suits feldspar that is milled in water or is already a slurry. Dry processing suits feldspar powder and granules and avoids a drying step. Reference: the Indian wet feldspar line in Morbi runs 200 mesh at 10–15 t/h with a Water Cooled Electromagnetic Separator 750 Model and reaches final whiteness of 75–85 (China standard). See Potassium Sodium Feldspar Magnetic Separator, 750 Water Cooling Wet Type Magnet and Electromagnetic Dry Powder Machine, or the feldspar application page.
Is Feldspar Magnetic? Why It Needs Iron Removal and How It Is Done: questions
Is feldspar magnetic?
Feldspar is not what the magnet picks up. The impurities that come with it, iron minerals, biotite, amphibole and tourmaline, are weakly magnetic and are removed with a high-intensity magnetic field and a high-gradient matrix.
Can magnetic separation make glaze-grade feldspar?
It can remove the magnetic iron. Vietnam’s TCVN 6598:2000 allows at most 0.3% Fe₂O₃ for glaze feldspar, and raw ore measured 0.51–1.00% in one Quang Nam study. Whether magnetic separation alone gets you there depends on how the iron occurs in your ore, so PTMS tests a 5–10 kg sample first.
How much can an electromagnetic separator reduce Fe₂O₃ in feldspar?
Typically about 30–70% where the iron is in free iron oxides, biotite or iron worn off equipment. Iron inside the mineral structure is not fully removed. These are ore-dependent ranges, not a guarantee.
Wet or dry processing for feldspar?
Wet suits feldspar milled in water or already a slurry; dry suits feldspar powder and granules and avoids drying. PTMS advises based on your plant.
What should I send for a feldspar test?
Send 5–10 kg of feldspar to the PTMS factory in Foshan. Within 5 days of receipt you get a report with before-and-after iron content and a recommended model. Also give particle size, capacity and target Fe₂O₃.
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