Iron Ore Tailings Slurry Density Reference
Preliminary context for iron ore tailings slurry density and percent solids — typical solids SG for a hematite/magnetite/quartz mix, broad % solids ranges by stage, and the relationship to pipeline pumping and thickener underflow. Educational only; not a tailings design standard.
Caution — preliminary orientation only
These are broad educational ranges, not site-specific tailings density values.
Iron ore tailings density and percent solids vary enormously with the ore body, iron mineralogy (hematite vs magnetite vs goethite), gangue content, grind size, rheology, plant design, and where in the circuit the sample is taken. The figures here are deliberately wide and are only meant to give a sense of scale. They are not a tailings design standard and must never be used as design figures. Tailings transport and storage design requires project testwork, plant samples, vendor data, and qualified engineering review under the relevant governance (e.g. ANCOLD guidance and the operation's own standards).
Purpose
Iron ore tailings are denser than most mineral tailings because iron oxides are heavy — hematite and magnetite both have a specific gravity around 5. This reference gives broad context for the slurry density and percent solids of iron ore tailings at different stages, so you can sanity-check a preliminary estimate before any plant data exists. Iron ore is core to Australian mineral processing (Pilbara and broader WA operations), and tailings handling there is a major design and water-balance concern. This is orientation only, not authority.
What changes tailings slurry density
- •Solids SG and mineralogy — a hematite/magnetite-rich tailings is much denser than a quartz-dominated one at the same percent solids.
- •Water fraction (percent solids) — the single biggest lever; more water means lower slurry density.
- •Grind size and gangue content — fines, clays, and silica change both the density and the rheology.
- •Circuit position — flotation tails, thickener underflow, pipeline, and deposited tailings all differ markedly.
Typical solids specific gravity
The mix of iron oxide and gangue sets the effective solids SG. Use the measured value for your ore where possible.
| Mineral / phase | Solids SG |
|---|---|
| Hematite (Fe₂O₃) | ~5.2 |
| Magnetite (Fe₃O₄) | ~5.1 |
| Goethite / limonite | ~3.3 – 4.3 |
| Quartz / silica gangue | ~2.65 |
| Typical tailings mix (iron + gangue) | ~3.0 – 4.5 |
Typical percent solids by stage
Percent solids (Cw) is by mass; slurry SG is the bulk specific gravity of the stream. Ranges overlap and are indicative only.
| Stage | % solids (Cw) | Slurry SG | Note |
|---|---|---|---|
| Flotation / process tailings | ~25 – 45% | ~1.2 – 1.5 | Relatively dilute stream leaving separation |
| Thickener underflow | ~50 – 70% | ~1.6 – 2.4 | Dewatered for pumping and water recovery |
| Pipeline transport (conventional) | ~30 – 55% | ~1.3 – 1.9 | Kept above deposition velocity |
| TSF deposited / settled | ~55 – 75%+ | ~1.7 – 2.4+ | After deposition and drainage; highly variable |
Relationship to pumping and thickener underflow
A denser tailings stream carries less water per tonne of solids, improving water recovery — but it raises the slurry SG, viscosity, and yield stress, so the pump must deliver more head and the pipeline must stay above its deposition velocity to avoid settling and blockage. Thickening the tailings (raising the thickener underflow density) is the usual lever for water recovery, but only up to the point where the underflow is still pumpable. Pump and pipeline design must use the actual tailings density and rheology — see Slurry Pump Head Sizing.
Why density alone does not define behaviour
Two tailings streams at the same density can behave completely differently. Density fixes the mass and buoyancy, but pumpability, deposition, beach slope, and settling are governed by rheology (yield stress, viscosity), particle size distribution, and clay content — none of which density captures. Never infer pumpability or deposition behaviour from density alone; it is necessary information, not sufficient.
Boundaries and exclusions
- •Educational ranges only — not site-specific, not design values, not a tailings design standard.
- •Does not model rheology, deposition, beach slope, or tailings storage facility (TSF) design.
- •Does not replace ANCOLD-aligned governance, geotechnical review, or vendor data.
- •Generic values must not be used for design — use project testwork and plant samples.
How to use in calculations
Take an effective solids SG for your tailings mix and a plausible percent solids for the stage, then enter them into the Slurry Density Calculator for a slurry density, or the Percent Solids Mass ↔ Volume Calculator to convert bases. Use the Slurry Mass Balance Calculator to split the stream into solids and water flows for a tailings water balance. Treat every result as preliminary and replace it with measured data. For broader context across ores, see the Typical Slurry Density Ranges Reference.
Source / context notes
- •Mineral densities follow standard references (hematite ~5.2, magnetite ~5.1, quartz ~2.65).
- •Tailings handling and slurry transport practice (e.g. Wills' Mineral Processing Technology; Wilson, Addie, Sellgren & Clift on slurry transport).
- •Australian tailings governance context: ANCOLD guidelines and operation-specific standards (cited for orientation, not reproduced here).
Compiled for orientation only. For any real calculation or design, use measured plant samples, project testwork, and vendor data reviewed by a qualified engineer.