Gravity Separation Testing for a Beach Sand Ilmenite Deposit
Beach sand ilmenite deposits can appear simple to process because the valuable minerals are already liberated by natural weathering and wave action. In practice, a reliable recovery flowsheet depends on much more than the presence of ilmenite in a bulk sample. Grain size, surface coatings, slimes, magnetic susceptibility, associated heavy minerals, and the distribution of titanium-bearing phases all influence separation performance.
Gravity separation testing provides an efficient way to understand how the heavy-mineral fraction behaves before committing to equipment selection or plant construction. The work can indicate whether spirals, shaking tables, centrifugal concentrators, or a combination of units will produce an acceptable ilmenite concentrate. It can also reveal when gravity recovery should be combined with magnetic separation or another cleaning stage.
For a mining operator, the objective is not simply to obtain a high assay in a laboratory product. The test program should establish mass yield, TiO₂ recovery, concentrate quality, water demand, circulating loads, and likely process risks. Those results form the basis for equipment sizing, operating conditions, and a practical beach-sand processing plant.
Why beach sand ilmenite needs careful testing
Ilmenite is commonly associated with rutile, zircon, monazite, garnet, quartz, feldspar, and other heavy or light minerals. Its specific gravity is higher than that of quartz, which makes gravity concentration possible, but the density difference may be less decisive when several heavy minerals occur together. Ilmenite may also be partially altered to leucoxene, changing its density, magnetic response, and surface behavior.
Natural deposits are rarely uniform across the entire mining area. Samples from the active beach, old strandlines, dunes, and wet lowlands may contain different proportions of slimes and heavy minerals. A single grab sample can therefore produce an attractive but misleading result. Representative sampling across mining blocks and vertical or lateral zones is essential for meaningful metallurgical conclusions.
The test program should also account for handling and preparation. If the feed contains clay, roots, shell fragments, or oversized debris, the laboratory procedure must reproduce the proposed washing and screening conditions. Even equipment maintenance can affect operating cost; for example, a review of wear part selection is useful when a project includes a hard, abrasive feed stage before scrubbing and classification.
Building a representative laboratory sample
Sampling begins with defining the deposit domains and estimating the tonnage represented by each sample. Incremental samples taken across a mining panel are generally more reliable than isolated material collected from a convenient location. Composite samples can represent a production blend, while variability samples show how the process responds to changes in grade, clay content, and particle-size distribution.
The laboratory should preserve the original moisture and particle-size characteristics as far as practical. Drying at excessive temperature can create agglomerates or alter surface coatings. Sample splitting must be performed with appropriate equipment so that heavy minerals do not segregate from lighter sand. A head sample should be retained for duplicate assays, mineralogical examination, and confirmation testing.
Important measurements include total heavy minerals, TiO₂, iron, silica, zirconium, rare-earth elements, moisture, and size distribution. Mineralogical examination using microscopy, automated mineralogy, or heavy-liquid methods can identify the proportion of liberated ilmenite and the presence of composite grains. This information explains why a gravity test may recover high mass but still produce a concentrate with unacceptable impurities.
Preparing the feed for gravity concentration
A typical test sequence starts with scrubbing or attrition to remove coatings and break weak aggregates. Desliming is often critical because very fine clay and weathered material can increase pulp viscosity, carry light gangue into the concentrate, and reduce the effective separation density. However, removing too much fine material may discard fine ilmenite, so the desliming cut point must be tested rather than assumed.
Wet screening separates the feed into practical size fractions, such as coarse sand, medium sand, and fine sand. Gravity equipment has an operating range in which particle size, density, and water flow interact effectively. Testing the entire feed as one fraction can hide the fact that coarse particles require a different device or that fine ilmenite needs a separate recovery circuit.
Representative preparation variables may include scrubber residence time, water addition, screen aperture, desliming cut size, and pulp density. The purpose is to distinguish mineralogical limitations from preparation problems. If recovery improves sharply after scrubbing, surface coatings or agglomeration are likely restricting separation. If the result changes mainly with desliming, fine gangue management deserves close attention in the plant design.
Comparing gravity equipment and test conditions
Laboratory gravity tests should use equipment that reflects the intended industrial circuit. A spiral can evaluate continuous roughing and scavenging behavior, while a shaking table can show the potential for a high-grade cleaning product. A centrifugal concentrator may be useful for fine heavy minerals, although its performance depends strongly on feed preparation and operating settings.
The main variables include feed rate, pulp density, wash water, splitter position, deck angle, spiral configuration, and the number of cleaning stages. Each test should record concentrate, middlings, and tailings weights, moisture, assays, and particle-size distributions. Water usage and circulating loads should be tracked because a result achieved with excessive dilution may be difficult to scale economically.
| Test focus | Key operating variables | Primary result | Design implication |
|---|---|---|---|
| Rougher gravity recovery | Feed rate, pulp density, wash water | Heavy-mineral recovery and mass pull | Determines whether gravity can provide an effective first concentration |
| Size-by-size response | Screen cut, desliming, classification | Ilmenite distribution by fraction | Indicates whether separate circuits are needed |
| Cleaner concentration | Table settings, spiral stages, splitter position | TiO₂ grade and impurity rejection | Defines concentrate quality and cleaning duty |
| Fine-particle recovery | Centrifugal force, fluidization water, feed density | Recovery of fine ilmenite | Shows whether fines require specialized equipment |
| Variability testing | Blended and domain samples | Stability across ore types | Supports operating range and plant risk assessment |
A single high-performing test is not enough to select equipment. Replicate runs should confirm repeatability, and the best conditions should be challenged with lower-grade or higher-slime material. The final flowsheet should be based on a balanced trade-off between recovery, concentrate grade, water consumption, and circuit complexity.
Interpreting recovery, grade, and product quality
Gravity test results are commonly evaluated through mass recovery, mineral recovery, concentration ratio, and separation efficiency. For ilmenite, the relevant product specification may be expressed as TiO₂ grade, total iron, chromium, silica, or other elements that affect downstream use. A high TiO₂ recovery can be commercially unattractive if the concentrate carries excessive zircon, monazite, garnet, or silica.
Partitioning by size is especially informative. Coarse liberated ilmenite may report readily to a spiral, while fine ilmenite may be lost to slimes or remain in middlings. Composite grains can also reduce grade because they behave according to their combined density rather than the density of pure ilmenite. These findings may justify a regrind-free cleaning circuit, additional classification, or a separate fine-mineral recovery stage.
Gravity concentration does not always provide the final separation required for mineral sands. Magnetic separation is frequently used after gravity upgrading because ilmenite is more magnetic than many associated minerals. Stronger magnetic stages may separate ilmenite from nonmagnetic zircon and rutile, while rare-earth-bearing minerals require careful control and responsible handling. If surface chemistry becomes important, a laboratory flotation program can complement the gravity work; the procedures described in a froth flotation test provide a useful comparison for evaluating kinetic response and reagent requirements.
Connecting testwork with plant engineering
Metallurgical results become valuable when they are translated into a complete process concept. A preliminary circuit may include feed reception, trommel or vibrating screen, scrubber, desliming cyclone, spiral roughers, scavengers, shaking-table cleaners, magnetic separation, concentrate dewatering, and tailings-water management. The exact arrangement depends on the feed size, mineral associations, production rate, and product specifications.
Water balance deserves early attention in beach-sand projects. Washing and gravity concentration can require substantial process water, while clay-rich feed may create difficult thickener and settling behavior. Recycling clarified water can reduce freshwater demand, but excessive recirculation may increase dissolved salts, fine solids, or process instability. Pilot-scale testing is valuable when water chemistry or tailings settling could affect continuous operation.
Engineering decisions should also include stockpile blending, modular construction, concentrate storage, environmental controls, and access to replacement parts. An integrated provider such as integrated plant solutions can connect ore testing with equipment selection, procurement, commissioning, and operational support. That connection helps prevent a common project failure: selecting individual machines successfully but overlooking how they interact as a complete circuit.
Practical recommendations for a defensible test program
- Collect composite and variability samples from all major geological and mining domains.
- Measure heavy-mineral content, TiO₂ distribution, mineral liberation, slimes, and particle size before testing.
- Test scrubbing, desliming, and size classification separately so preparation effects are visible.
- Compare rougher, scavenger, and cleaner gravity stages using mass-balanced assays.
- Confirm the preferred circuit with variability samples, water-balance data, and a pilot-scale campaign where justified.
A strong report should present the complete mass balance, test conditions, assay methods, product photographs or mineralogical observations, and losses by size fraction. It should explain why the selected equipment is appropriate and identify the conditions that could reduce recovery in operation. This level of documentation supports financing, permitting, equipment procurement, and realistic production forecasting.
Gravity separation testing for a beach sand ilmenite deposit is most effective when it is treated as a decision-making program rather than a single laboratory exercise. Representative samples, controlled preparation, size-specific testing, and independent confirmation can reveal the practical recovery envelope before capital is committed.
For project stakeholders moving toward a production decision, the next step is to combine the metallurgical balance with mine planning, water management, equipment sizing, and commissioning requirements. Contact Lozova to develop an ore-testing and process-engineering program suited to the deposit’s mineralogy, target concentrate, and operating conditions.