MINERAL PROCESSING KNOWLEDGE · GRAVITY SEPARATION
Compare jigs, spiral concentrators and shaking tables by separation principle, feed size, capacity, operating conditions and typical duties in mineral processing.
Technical overview. Actual process selection depends on representative ore samples, mineralogy, testwork and site conditions.
Jigs, spiral concentrators and shaking tables are all used in gravity concentration, but they do not perform the same duty. Each separates particles using differences in settling behaviour and density, while also responding to particle size, shape, slurry conditions and feed stability. A practical circuit may use one device, several devices in series, or separate equipment for different size fractions.
Technical note: There is no universal particle-size cut-off that makes one gravity separator suitable for every mineral. The ranges overlap and depend on density contrast, particle shape, liberation, feed rate, water conditions and equipment design. Treat the comparison below as a screening guide, then confirm selection with representative tests.
1. Jigging: pulsating water and stratification
A jig separates particles in a bed using a repeated upward and downward water movement. The pulsation causes particles to rearrange and stratify according to their settling behaviour, density and size. Heavier particles tend to concentrate in the lower part of the bed and can be discharged separately from lighter material. Jigs are commonly considered for coarse to intermediate size fractions where the feed can be controlled and the density contrast is sufficient.
- Potential duties: coarse chromite, cassiterite, manganese and other heavy mineral feeds.
- Strengths: continuous operation, relatively high capacity in suitable duties, and ability to treat a defined size fraction.
- Limitations: performance can be affected by wide size distributions, near-density material, clay, slimes and unstable feed conditions.
- Key checks: feed classification, bed depth, pulsation, water rate, particle size and density distribution.
2. Spiral concentrators: flowing-film separation
A spiral concentrator uses a flowing slurry film moving down a helical channel. Particles separate through the combined effects of gravity, water flow, centrifugal effects and friction. The exact movement depends on particle density, size, shape, slurry concentration and spiral geometry. Spirals are often used for fine to intermediate heavy-mineral duties and can be installed in multiple banks when large tonnages must be treated.
- Potential duties: suitable chromite, tin, mineral sands and other heavy-mineral feeds.
- Strengths: compact arrangement, no moving drive parts in the separation channel, and potential for multiple units in parallel.
- Limitations: feed size range, slurry density, water balance and particle shape can influence separation; very fine slimes may reduce selectivity.
- Key checks: size classification, feed solids, wash water, splitter settings and middlings recycle.
3. Shaking tables: flowing film plus deck motion
A shaking table combines a sloped deck, a repeated table motion and wash water. Particles move across the deck while stratifying according to density and size. The operator can separate concentrate, middlings and tailings along different discharge zones. Tables are often used for cleaning or upgrading smaller streams rather than treating the full high-tonnage plant feed.
- Potential duties: upgrading jig or spiral concentrates, cleaning cassiterite or gold concentrates, and laboratory or small-scale separation tests.
- Strengths: visible separation zones and the ability to produce distinct concentrate, middlings and tailings streams.
- Limitations: relatively low capacity per unit, careful feed preparation is needed, and operator settings affect separation.
- Key checks: feed size range, pulp density, water flow, deck slope, stroke and splitters.
4. Side-by-side comparison
| Selection factor | Jig | Spiral concentrator | Shaking table |
|---|---|---|---|
| Main action | Pulsating fluidization and bed stratification | Flowing film on a helical channel | Flowing film on a moving deck |
| Typical circuit duty | Coarse / intermediate gravity recovery | Intermediate / fine heavy-mineral separation | Cleaning or upgrading a smaller stream |
| Capacity approach | Often selected for higher-tonnage size fractions | Often installed in banks and parallel units | Usually lower capacity per unit |
| Operational sensitivity | Feed sizing, pulsation, bed and water | Feed solids, size distribution and wash water | Feed rate, deck motion, slope and water |
| Common limitation | Wide size ranges and slimes can impair separation | Very fine slimes and feed instability | Lower throughput and need for controlled feed |
5. Why classification usually comes first
A gravity separator does not see only density. It also responds to particle size, shape and settling behaviour. If a feed contains very coarse and very fine material together, size effects can interfere with density separation. Screening, desliming or classification may therefore be needed before selecting the separator. Different size fractions may be routed to different units.
6. A practical equipment selection sequence
- Characterize the valuable mineral and the main gangue minerals.
- Measure the feed size distribution and identify clay or slimes.
- Check the density contrast and liberation of the valuable mineral.
- Separate the feed into suitable size fractions where necessary.
- Run gravity tests using the likely equipment types or representative laboratory methods.
- Compare concentrate grade, recovery, mass pull, water use and the amount of middlings.
- Select the circuit and recycle strategy only after reviewing the mass balance.
7. Examples by mineral
A coarse alluvial tin or chromite feed may be considered for washing, classification and jigging. A finer classified heavy-mineral stream may be considered for spiral concentration. A table may then upgrade a smaller concentrate stream. Gold circuits can use jigs or other gravity units for liberated coarse gold and tables for concentrate cleaning. These are examples of possible duties, not standard recipes.
Explore the current Jigging Machine, Spiral Chute and Shaking Table pages, then compare the mineral-specific requirements in the Tin Ore Processing and Chrome Ore Beneficiation guides.
Conclusion
Choose a gravity separator by duty, not by name. Jigs, spirals and shaking tables can complement one another when the feed is classified and the process is designed around the mineral’s size and density characteristics. Representative ore testing and a size-by-size mass balance are the right basis for a purchase decision.
Need help comparing gravity equipment for your ore? Send your ore type, feed size and capacity.