Mineralogy sets the magnetic route
Required field intensity depends on the susceptibility of value and gangue minerals. Low intensity suits strongly magnetic magnetite; fine hematite often needs high-gradient separation.
Magnetite, hematite, goethite, clays and silica should be quantified across expected feed types.
Liberation before field intensity
A stronger field cannot fully correct locked hematite-silica particles. Grinding must create liberation without excessive slimes and lost capacity.
Size-by-size testing can identify fractions suited to dry, wet, gravity or magnetic treatment.
Key test variables
Field strength, matrix, gap, passage speed, solids, wash water and stage arrangement all affect grade and recovery. HGMS matrices create strong local gradients for weakly magnetic particles.
Testing should build grade-recovery curves across several conditions.
- Field intensity and gradient
- Size and liberation
- Matrix and passage speed
- Solids and wash water
- Rougher and cleaning stages
Dry, wet or combined circuits
Dry separation may suit coarse feed and water-limited sites, while wet treatment handles fines more effectively but adds water and dewatering duties.
Gravity pre-concentration, selective grinding and HGMS may form an efficient combined route for some hematite ores.
Scale-up to the plant
Industrial design must cover feed distribution, pressure drop, matrix washing, blockage and maintenance access.
Operating settings should be reviewed as feed mineralogy changes rather than treated as fixed values.
FAQ
Frequently asked questions
Can hematite be recovered with low intensity?
Hematite is weaker than magnetite and fine low-grade material commonly needs high intensity or HGMS, depending on liberation.
Why can higher field reduce product grade?
It can capture more weakly responsive gangue and composite particles while raising recovery.
Is dry or wet separation better?
It depends on size, moisture, water availability, mineralogy and product targets.
REFERENCES
Technical sources
Sources are provided for further technical reading. Final engineering decisions require project-specific testwork.