The Ultimate Guide to Gold Gravity Beneficiation

Chemical gold extraction is effective but often involves high costs and serious environmental risks. The expense of reagents and strict regulations can quickly erode your profits. Gravity separation offers a simpler, cheaper, and greener path.

Gravity separation is a chemical-free method that uses the high density of gold to separate it from lighter waste rock. It is the most cost-effective choice for ores where gold particles are physically liberated and large enough to be recovered.

This technique leverages a fundamental law of physics. It’s the oldest method of gold recovery, refined with modern technology. For the right ore body, a gravity circuit is the most direct and profitable way to produce a high-grade gold concentrate without purchasing a single drum of cyanide.

What is the Principle of Gold Gravity Separation?

The concept of gravity separation seems almost too simple. How can just water and movement effectively separate microscopic specks of gold from tons of rock? The answer lies in one of nature’s most basic and reliable forces.

The principle is the significant density difference between gold and waste rock. In a fluid medium like water, heavy gold particles settle much faster than the lighter gangue minerals, allowing them to be captured and concentrated.

This is the same principle a prospector uses with a gold pan. Our modern machines just apply this principle on an industrial scale with much higher efficiency. Understanding this core concept is the first step to designing a successful Gold Ore Beneficiation circuit.

The Physics of Separation

The effectiveness of gravity separation depends on a few key factors. It’s a science of managing density, particle size, and water flow.

• The Role of Density: This is the most critical factor. Gold has a specific gravity of 19.3 g/cm³, making it exceptionally dense. By contrast, common waste minerals like quartz and feldspar have a specific gravity of around 2.6-2.7 g/cm³. This huge difference means that in a moving slurry, gold has a strong tendency to settle and report to the bottom, while the lighter gangue is easily washed away.
• The Influence of Particle Size and Shape: While density is key, particle size and shape also play a role. A very large particle of light quartz can sometimes settle at the same rate as a very fine particle of gold. Similarly, a flat, flaky gold particle will behave differently than a round, “shotty” one. This is why classifying the feed into different size fractions is so important for efficient recovery.

Mineral	Specific Gravity (g/cm³)	Behavior in Slurry
Gold	19.3	Settles very quickly
Pyrite	5.0	Settles moderately fast
Magnetite	5.2	Settles moderately fast
Quartz	2.7	Settles slowly, easily washed away

What are the steps involved in a complete gold gravity separation process?

Many people mistakenly believe that buying a single machine is enough. This leads to poorly designed circuits that lose significant amounts of gold and money. A truly effective system is a sequence of carefully planned stages.

A complete gravity process includes washing and screening to remove clays and classify sizes, a primary concentration stage to capture the bulk of the gold, and a secondary cleaning stage to upgrade the concentrate to a high purity.

Each step in the process has a specific job. Skipping a stage or using the wrong equipment will create a bottleneck and send your profits directly to the tailings dam.

The Four Core Stages of a Gravity Circuit

A professional Gold Processing Plant is designed as an integrated system, not just a collection of machines.

1. Liberation & Washing: For Placer Gold Mining, this involves using a trommel screen or log washer to break down sticky clays and wash the gold-bearing gravel. For hard rock, this means crushing and grinding to free the gold from the solid rock. This stage is about preparing the material for recovery.
2. Size Classification: After washing, the slurry is often passed through screens or Hydrocyclones. This separates the feed into different size fractions. Treating coarse particles and fine particles in separate, specialized circuits dramatically increases overall recovery.
3. Primary Concentration: This is where the bulk of the gold is captured from the main slurry stream. Machines like Jigging Separators or Spiral Chutes are used for high-volume, coarse material, while Centrifugal Concentrators are used for fine gold.
4. Concentrate Cleaning: The material from the primary stage is a low-volume, medium-grade concentrate. It is then sent to a final cleaning stage, almost always a Shaking Table, to produce a very high-grade final product ready for smelting.

Jigs, shaking tables, and centrifugal concentrators—which one should I choose?

There are many types of gravity separation equipment available. Choosing the wrong one for your specific ore and particle size is a common mistake that guarantees poor gold recovery and wasted investment.

Choose your equipment based on particle size and the specific application. Jigs are for coarse, high-volume feeds. Centrifugal concentrators excel at fine gold recovery. Shaking tables are for cleaning small batches of pre-concentrated material.

These machines are not interchangeable. They are specialized tools. A well-designed circuit often uses two or even all three in combination to maximize recovery across the entire range of gold particle sizes.

Equipment Selection Guide

Thinking of these machines as a team is the best approach. Each one plays a different position.

• The Bulk Player (Jig): A Jigging Separator is a workhorse. It pulses water up through a bed of material, allowing heavy particles to sink while light ones are washed away. It’s perfect for handling large volumes of gravel and recovering coarse gold, but it will lose most of the fine gold.
• The Fine Gold Specialist (Centrifugal Concentrator): A Centrifugal Concentrator spins a bowl at high speed, creating an artificial gravity field up to 200 times that of Earth’s. This incredible force allows it to capture microscopic gold particles that other machines would lose. It’s essential for any operation serious about fine gold recovery.
• The Finisher (Shaking Table): A Shaking Table is a finishing tool, not a primary recovery device. It takes the small amount of concentrate from the jigs and centrifuges and performs the final upgrade, separating the gold from other heavy minerals to produce a smelt-ready product.

Equipment	Best For	Advantages	Limitations
Jigging Separator	Coarse particles (+1mm), high-volume feeds.	High capacity, low operating cost.	Inefficient at recovering fine gold (<200 microns).
Centrifugal Concentrator	Fine particles (1mm down to 10 microns).	Extremely high recovery of fine gold.	Lower throughput than jigs, requires clean water.
Shaking Table	Final cleaning of pre-concentrated material.	Produces very high-grade concentrate.	Very low capacity, cannot treat the main plant feed.

Why am I only recovering coarse gold, and where has all the fine gold gone?

This is a classic problem that haunts many gold mining operations. You can see nuggets and coarse flakes in your sluice, but the final weight of your gold bar is much lower than expected. That missing profit is almost always in the form of lost fine gold.

Fine gold is lost because it is not properly liberated, the recovery equipment is not designed for its small size, or the slurry is too thick with clays. Over-grinding can also create ultra-fine “slime” gold that floats away.

Fine gold has a very high surface-area-to-mass ratio. In a slurry, it behaves less like a rock and more like a leaf, staying suspended in the water and flowing right out to your tailings dam. Capturing it requires a dedicated strategy.

Strategies for Improving Fine Gold Recovery

You must actively hunt for fine gold; it will not simply fall into your concentrate box.

• Liberate, Don’t Annihilate: For hard rock ores, the goal of grinding is to free the gold, not pulverize it. Grinding too fine creates “slimes” that are impossible for gravity equipment to catch. Use a staged grinding approach: grind coarsely, recover the liberated gold immediately with a centrifuge, and only then re-grind the tailings for further processing.
• Install the Right Tools: Sluices and jigs are not effective for fine gold. To capture particles smaller than 150 microns, you must install an enhanced gravity device like a Centrifugal Concentrator in your circuit. This is not optional if you want to maximize your recovery rate.
• Attack the Slurry Viscosity: Your enemy is often the slurry itself. If your ore contains clays, they will absorb water and make the slurry thick like molasses. This high viscosity prevents fine gold from settling. You must attack the clay by using rotary scrubbers or log washers at the front of your plant and by carefully controlling your water balance to maintain a low slurry density.

What core equipment is needed to build a 500 TPD placer gold gravity separation line?

Scaling up from a small prospecting setup to a commercial operation is a major step. A 500 tonnes per day (TPD) plant requires a robust, integrated system to handle large volumes efficiently and profitably.

A 500 TPD placer gold line requires a feeder, a trommel screen for washing and sizing, primary concentrators like jigs for bulk recovery, and a finishing circuit with centrifugal concentrators and shaking tables for fine gold capture.

The exact equipment list depends on the ore’s characteristics, like clay content and gold size distribution. However, a standard, professional plant layout includes several core components working in sequence.

Core Equipment for a 500 TPD Placer Plant

Building a plant of this size is a major capital project. Each component must be correctly sized to avoid bottlenecks and ensure smooth operation.

Function	Core Equipment	Description
Feeding & Washing	Grizzly Feeder, Trommel Screen	The feeder provides a controlled flow of material. The trommel’s rotating action aggressively washes and breaks down clays, while screening separates oversized rocks from the valuable slurry.
Bulk Concentration	Jigging Separator Machine	These machines treat the entire slurry flow from the trommel. They are designed to recover the majority of the coarse and mid-sized gold at a high throughput rate.
Fine Gold Recovery	Centrifugal Concentrator	This is the profit center for fine gold. It treats the tailings from the jigs or a specific fine-size fraction to capture the valuable gold that would otherwise be lost.
Concentrate Cleaning	Shaking Table	All concentrates from the jigs and centrifuges are sent here. The shaking table performs the final upgrade, creating a high-purity gold product ready for smelting.
Support Systems	Slurry Pumps, Conveyors, Water Pumps	These components transport material between stages and manage the large volumes of process water, often including a recycling system to reduce costs.

How is the gravity process for hard rock gold different from placer gold?

The word “gold” is the same, but the ore is completely different. Applying a placer mining process to a Hard Rock Gold Mining deposit will result in total failure. The fundamental difference lies in one critical word: liberation.

The key difference is the extensive crushing and grinding circuit required for hard rock ore. This energy-intensive stage is necessary to physically liberate the gold particles from the host rock before any gravity separation can work.

Placer gold has been liberated by millions of years of natural erosion. In hard rock mining, we must replicate this process in a matter of minutes using powerful machinery. This makes hard rock plants more complex and capital-intensive.

Key Process Differences

The flowsheets for these two ore types are fundamentally distinct.

• The Front-End: A placer plant starts with washing and scrubbing. A hard rock plant starts with a multi-stage Crushing Plant, using Jaw Crushers and Cone Crushers to reduce large rocks down to a gravel size.
• The Liberation Stage: Placer ore needs none. Hard rock ore must be ground, typically in a Ball Mill, to a fine sand or powder consistency. This is often the single largest consumer of power in the entire plant.
• The Role of Gravity: In placer operations, gravity is often the only recovery method used. In hard rock circuits, gravity concentrators are typically placed within the grinding circuit. Their job is to intercept and recover coarse gold as soon as it is liberated, preventing it from being over-ground and lost. The tailings from the gravity circuit may then be sent to other processes like flotation or leaching.

Feature	Placer Gold Process	Hard Rock Gold Process
Liberation	Natural, requires only washing.	Mechanical, requires an expensive crushing and grinding circuit.
Core Equipment	Trommel, Jigs, Shaking Table.	Crushers, Ball Mill, Centrifugal Concentrator, Pumps, Cyclones.
Complexity	Relatively simple and low-tech.	Complex, high-energy, requires sophisticated controls.

How pure is the gold concentrate from gravity separation, and does it need further processing?

The final product from your gravity circuit is not a shiny gold bar. It is a heavy, dark-colored concentrate. Understanding what to do with this product and how much it is worth is a critical part of the business plan.

Gravity concentrate is not pure gold. Its gold content can range from 1% to over 70%, depending on the type of ore and the efficiency of concentrate purification. This concentrate must be smelted to produce the final gold-silver alloy ingot.

The purpose of the gravity circuit is to remove the maximum amount of waste rock with the minimum amount of equipment and cost. This leaves a small volume of high-value material that can be economically processed into its final form.

From concentrates to honeysuckle

The journey is not over when the gold is captured.

1. Final Upgrading: The primary concentrates are passed over a Shaking Table. A skilled operator can use the table to “fan” the material out, separating the brilliant yellow band of gold from the other heavy minerals like pyrite and magnetite. This produces the final, high-purity concentrate.
2. Smelting: This high-grade concentrate is then dried and mixed with special chemicals called fluxes (such as borax, soda ash, and silica). The mixture is heated in a furnace to over 1100°C. The fluxes bind with the remaining impurities, forming a molten glass-like layer called slag. The much denser molten gold sinks to the bottom.
3. Pouring: The furnace is tilted, and the molten gold is poured into a mold, leaving the slag behind. When it cools, you have a gold doré bar, which is an alloy of gold and any silver that was present in the ore. This bar can be sold directly to a professional refinery for final purification.

How much does a set of gravity separation equipment cost?

This is a critical question for any potential investor. The budget for a Gold Processing Plant can vary dramatically, and it is important to understand what drives the cost before making a commitment.

The cost can range from a few thousand dollars for a small, portable testing plant to several million dollars for a large-scale, fully integrated processing line. The primary cost drivers are processing capacity (tons per hour) and ore complexity.

There is no single “price list” for a processing plant. The final cost is determined by a custom-engineered solution tailored to your specific project needs. As a manufacturer, we work with you to design a system that fits your budget and production goals.

Factors That Determine Equipment Cost

Getting a reliable quote requires a detailed discussion about your specific project.

• Processing Capacity: This is the biggest factor. A 100 ton-per-hour (TPH) plant will be significantly more expensive than a 10 TPH plant because every piece of equipment—from the feeder to the pumps—must be larger and more robust.
• Ore Type: A Placer Gold Mining plant is generally much cheaper than a Hard Rock Gold Mining plant of the same capacity. This is because the hard rock plant requires the addition of an expensive crushing and grinding circuit (Jaw Crusher, Cone Crusher, Ball Mill).
• Manufacturer and Automation: The level of automation, the quality of components (e.g., motors, wear parts), and the manufacturer’s location and reputation also influence the price. As a factory-direct supplier, we can offer competitive pricing by eliminating intermediary costs.

Scale	Typical Capacity	Estimated Cost Range (USD)	Key Equipment
Small/Artisanal	1-5 TPH	$10,000 – $50,000	Small Trommel, Sluice/Centrifuge, Shaking Table
Medium Placer	50-100 TPH	$150,000 – $500,000	Feeder, Large Trommel, Jigs, Centrifuges, Pumps
Medium Hard Rock	10-20 TPH	$400,000 – $1,500,000+	Full Crushing/Grinding Circuit, Centrifuges, Pumps

Conclusion

Gravity separation is a powerful, cost-effective, and environmentally friendly method for gold extraction. Success requires proper ore analysis, a well-designed flowsheet, and the correct selection and operation of equipment to capture both coarse and fine gold.