Alluvial gold processing is one of the simplest and most cost-effective methods of gold extraction. Unlike hard-rock mining, alluvial mining targets gold found in riverbeds, floodplains, and ancient stream channels. Because the gold is already liberated from the host rock, miners can use simple gravity-based methods to achieve high recovery rates with low operational costs.

This guide explains the full workflow of alluvial gold processing, the principles of placer gold separation, and the best equipment for different production scales.

1. What Is Alluvial Gold?

Alluvial gold refers to gold particles transported and deposited by water movement. It appears in the form of:

• Nuggets

• Flakes

• Fine gold

• Micron gold mixed with sands and gravels

These deposits are usually shallow, making them easy to access with minimal excavation. Because the gold is free and not chemically bound to other minerals, processing relies mainly on gravity separation.

2. Key Principles of Alluvial Gold Processing

Alluvial gold extraction follows three basic principles:

a. Screening and classification

Raw material must be washed to remove clay, stones, and oversized material. Proper classification ensures stable recovery in downstream separation equipment.

b. Gravity separation

Since gold has a high density (19.3 g/cm³), placer gold separation focuses on separating heavy gold from lighter sands using water movement and gravity.

c. Concentration and final refining

After rough concentration, fine gold is upgraded using specialized concentrate equipment to achieve high purity.

These principles apply to both small-scale and large-scale alluvial operations.

3. The Complete Alluvial Gold Processing Workflow

Step 1: Feeding and washing

Purpose: Break up clay, remove stones, and wash gold-bearing material.
Common equipment:

• Trommel scrubber

• Rotary wash plant

• Vibrating screen

• Log washer

Trommel scrubbers are ideal for sticky clay-rich alluvial deposits, ensuring effective separation before classification.

Step 2: Screening and classification

The washed ore is classified into different particle sizes.
Why it matters:

• Gold recovery depends on consistent feed size.

• Prevents overloading of concentrators.

Screens can be designed with multiple layers to process fine and coarse materials simultaneously.

Step 3: Primary gravity separation

This is the core of placer gold separation.
Equipment options:

• Sluice boxes

• Centrifugal concentrators

• Jig machines

Sluice boxes are widely used in riverside placer mining, while centrifugal concentrators (such as Knelson or similar types) achieve very high recovery for fine gold.

Step 4: Fine concentration

This step upgrades the concentrate into a high-grade gold product.
Best equipment:

• Shaking table

• Miller table

• Gold amalgamation barrel (used less today due to mercury regulations)

Shaking tables are the most effective, offering excellent separation accuracy for both medium and fine gold.

Step 5: Final refining

After concentration, the gold may undergo:

• Smelting

• Electrolytic refining

• Chemical purification (depending on purity requirement)

Small operations typically melt the concentrate directly into gold bars.

4. Best Equipment for Alluvial Gold Processing

Below is the most commonly used and most effective equipment list, depending on deposit type and production scale.

a. Trommel scrubber / gold wash plant

Ideal for sticky or clay-rich alluvial deposits.
Features:

• High washing efficiency

• Large processing capacity

• Low maintenance

b. Sluice box

Great for coarse gold and river mining.
Benefits:

• Simple structure

• Low cost

• Long service life

Adding carpet or matting improves gold capture.

c. Centrifugal concentrator

One of the most effective devices for fine gold recovery.
Advantages:

• High recovery rate (up to 95%+)

• Suitable for both fine and ultra-fine gold

• Small footprint

d. Jig machine

Best for medium-sized gold particles.
Advantages:

• High processing capacity

• Low water consumption

• Good for coarse gold nuggets

e. Shaking table

Essential for final gold concentration.
Benefits:

• Precise separation

• Excellent for fine gold

• Produces high-grade concentrate

f. Magnetic separator (optional)

Useful if the deposit contains magnetic black sand, helping improve final purity.

5. How to Choose the Right Alluvial Gold Processing Plant

To ensure high recovery and low operation cost, consider:

Ore type and clay content

• High clay → trommel scrubber + centrifugal concentrator

• Clean sand → vibrating screen + sluice + shaking table

Gold particle size

• Coarse gold → sluice or jig

• Fine gold → centrifugal concentrator + shaking table

Production capacity

• Small-scale (1–20 TPH): portable wash plants

• Medium-scale (20–200 TPH): modular trommel + centrifugal system

• Large-scale (200+ TPH): custom-designed processing plant

Water supply and site conditions

Choose water-efficient systems if water is limited, or use recycling tanks.

6. Tips for Maximizing Recovery in Placer Gold Separation

• Keep equipment level and stable during operation.

• Maintain consistent feed size and feed rate.

• Use the right riffles or mats in sluice boxes.

• Reprocess tailings if gold is fine; fine gold often remains.

• Test different recovery systems during pilot runs.

Proper calibration is essential for capturing the highest possible percentage of gold.

Conclusion

Alluvial gold processing is efficient, cost-effective, and suitable for miners of all scales. By understanding deposit characteristics, applying the correct placer gold separation methods, and selecting the right equipment—from trommel scrubbers and sluice boxes to centrifugal concentrators and shaking tables—you can achieve high recovery rates and maximize profitability.