Gold Processing Methods: Flotation vs. Gravity Separation vs. Cyanidation

1000tpd-gold-process

Today, the most widely used gold extraction methods include gravity separation, flotation, and cyanidation, each serving distinct roles depending on mineralogy, particle-size distribution, and economic constraints. This article provides a complete guide to gold flotation and integrates a detailed comparison of flotation vs. gravity vs. cyanidation. 

1.1 What Is Gold Flotation?

Gold flotation is a mineral beneficiation process that separates gold-bearing sulfides and fine gold particles using differences in surface hydrophobicity. Chemical reagents make gold and sulfide minerals hydrophobic, causing them to attach to air bubbles and float to the surface of flotation cells. The froth concentrate produced is then sent to downstream processing such as cyanidation or oxidation.

Flotation is the dominant method for sulfide-rich, fine-grained, and polymetallic gold ores.

1.2 The Gold Flotation Flowsheet

A typical flotation circuit involves:

1. Crushing and Grinding

Ore is crushed and ground to 75–90% passing 75 μm to liberate gold-bearing minerals.

2. Conditioning

Reagents are added, including:

• Collectors (xanthates, dithiophosphates)

• Frothers (MIBC, pine oil)

• pH modifiers (lime)

• Depressants and activators (CuSO₄)

3. Rougher Flotation

High recovery of gold-bearing sulfides.

4. Scavenger Flotation

Captures residual gold from rougher tailings.

5. Cleaner Flotation

Upgrades concentrate to a high-grade product.

6. Concentrate Dewatering

Thickeners and filters remove water before cyanidation or oxidation.

Flotation recoveries typically range from 85% to 95%, depending on ore type and mineral chemistry.

Before comparing, it is essential to define the two other major methods: gravity separation and cyanidation.

2.1 Gravity Separation for Gold

Gravity separation relies on density differences between gold (specific gravity ≈19.3) and gangue minerals.

Common equipment includes:

• Shaking tables

• Jig concentrators

• Spiral chutes

• Centrifugal concentrators (Falcon, Knelson)

Best suited for:

• Coarse free gold (>0.1–0.2 mm)

• Placer and alluvial gold deposits

• Free-milling ores with minimal sulfides

Gravity recovery is usually 40–80%, depending on gold size distribution.

2.2 Cyanidation for Gold

Cyanidation dissolves gold using sodium cyanide under controlled alkaline conditions. Gold in solution is then adsorbed onto activated carbon (CIP/CIL) or precipitated.

Best suited for:

• Free-milling, well-liberated gold

• Oxide gold ores

• Flotation concentrates

• Whole-ore leaching in high-grade deposits

Recoveries typically reach 85–98%, making it the highest-yielding method overall..

3.1 Recovery Efficiency

Key takeaway:

• Gravity works only for coarse gold.

• Flotation excels with fine and sulfide-rich ores.

• Cyanidation is the most complete extraction method when gold is exposed.

3.2 Particle Size Performance

Flotation provides the widest range of effective particle-size recovery, especially for fine gold.

3.3 Ore Type Suitability

3.4 Capital and Operating Cost Comparison

Gravity Separation

• Low CAPEX

• Very low OPEX

• Minor maintenance

• No chemicals required

Flotation

• Moderate CAPEX (grinding + flotation cells)

• OPEX includes reagents and energy

• Skill-dependent operation

Cyanidation

• High CAPEX (CIL tanks, detox, carbon regeneration)

• High OPEX due to cyanide, lime, detox chemicals

• Strict environmental controls required

Flotation sits between the two extremes—more complex than gravity, less expensive than full cyanide circuits.

Most high-performance operations no longer rely on a single method. Instead, they integrate multiple processes to maximize recovery and reduce costs.

4.1 Gravity + Cyanidation

This classic free-milling flowsheet is common in many gold mines.

Advantages:

• Gravity removes coarse gold early

• Cyanidation recovers fine liberated gold

• Lower cyanide consumption

• Lower carbon fouling

Used widely in:

• Oxide gold deposits

• Greenstone belt gold mines

• Medium-grade vein deposits

4.2 Flotation + Cyanidation (Most Common for Modern Sulfide Ores)

This flowsheet concentrates sulfides before leaching.

Benefits:

• Reduces ore mass entering expensive leaching circuits

• Achieves high recoveries from fine, sulfide-hosted gold

• Suitable for gold–copper and gold–zinc systems

Cyanidation is performed on flotation concentrate, not whole ore, reducing reagent consumption significantly.

4.3 Gravity + Flotation + Cyanidation (All-in-One Flow)

This advanced flowsheet is ideal for complex ore bodies.

Process logic:

1. Gravity first removes coarse gold.

2. Flotation upgrades sulfides containing fine gold.

3. Cyanidation leaches the concentrate for maximum recovery.

This integrated approach can achieve 90–98% total gold recovery, even in challenging mineralogies.

Gravity Separation

Advantages:

• Lowest cost

• Eco-friendly

• Simple operation

Disadvantages:

• Only effective for coarse gold

• Poor for sulfides or ultrafine particles

Flotation

Advantages:

• Excellent for fine and refractory gold

• Produces high-grade concentrates

• Essential for polymetallic systems

Disadvantages:

• Complex reagent management

• Sensitive to pulp chemistry

• Requires sulfide tailings management

Cyanidation

Advantages:

• Highest total recovery

• Mature, proven technology

• Effective for a wide range of ore types

Disadvantages:

• High cost

• Environmental restrictions

• Requires gold to be exposed (liberated)

The global shift toward deeper, lower-grade, and more complex gold deposits has made gold flotation and integrated processing flowsheets more important than ever. While gravity separation provides a low-cost solution for coarse free gold, and cyanidation delivers the highest total recovery for liberated gold, flotation remains the most versatile and effective method for fine, sulfide-rich, and polymetallic gold ores. Modern plants frequently combine gravity, flotation, and cyanidation to optimize recovery, reduce reagent costs, and manage environmental impacts.