Gold Extraction from Oxidized Ore: Analysis of 4 Mainstream Processes

Oxidized gold ore is the backbone of the global gold industry. Nature has done the hard work, breaking down tough sulfide minerals and making the gold chemically accessible. But this “easy” ore is full of traps.

Choosing the right gold extraction process is not about theory; it is about matching the technology to your ore’s physical and chemical properties. The key is to understand your ore’s grade, particle size, and especially its clay content before you decide.

The biggest challenge in most oxidized gold ore processing is not chemistry, it is physicality. Specifically, clay. Clay will choke your process and steal your profits faster than a bad assay. Let’s look at the four main approaches and the hard-won lessons that go with each.

What key properties of oxidized gold ore must be analyzed before choosing an extraction process?

Do not buy a single piece of equipment until you have answered these questions. The answers will dictate your entire flowsheet and business model.

Before any decision, a detailed mineral processing test is mandatory. It must determine the ore’s head grade, gold particle size distribution, clay content and type, and cyanide leach characteristics. This data is non-negotiable.

These are the vital signs of your ore body.

Critical Ore Characteristics

• Gold Grade (g/t): This is the most basic factor. High-grade ore can justify a high-cost, high-recovery process like CIL. Low-grade ore can only be profitable with a low-cost process like heap leaching.
• Gold Particle Size: Is the gold coarse and free (“gravity gold”) or is it microscopic and disseminated throughout the rock? This will determine if a gravity circuit is viable and how fine you need to grind the ore.
• Clay Content & Permeability: This is the hidden killer. High clay content will make heap or vat leaching impossible without agglomeration. It dictates whether you can leach a pile of rocks or if you must create a slurry.
• Leach Kinetics & Reagent Consumption: How fast does the gold dissolve in cyanide? How much cyanide and lime does the ore consume? Some ores are “preg-robbing,” containing natural carbon that steals gold from the solution, requiring a specific process like CIL to overcome.

Process 1: Heap Leaching – What types and scales of gold mines is it suitable for?

This is a game of scale and patience. It is the definition of a low-cost, bulk tonnage operation.

Gold heap leaching is ideal for large-scale, low-grade (<1.5 g/t) oxidized gold mines. Its success depends entirely on the ore’s permeability, which is its ability to allow the cyanide solution to trickle through the stacked heap.

Heap leaching has the lowest capital cost per ton, but it comes with trade-offs.

Heap Leaching: Key Considerations

Aspect	Description	Operational Insight
The Process	Crushed ore is stacked on a lined pad and irrigated with a weak cyanide solution. The gold-bearing solution is collected and processed.	A slow process. Recovery takes months or years. You sacrifice speed and some recovery for low upfront cost.
Critical Failure Point	Poor Permeability. Clay and fine particles can block the spaces within the heap, preventing the solution from contacting the ore. This creates “channeling” and leaves large parts of the heap unleached.	Agglomeration is not optional. For ore with any clay, tumbling it with cement binder and cyanide in a drum is essential. This creates durable pellets, locking in the fines and preserving the heap’s permeability.
Best For	Massive, low-grade deposits where you can move mountains of material cheaply. The ore must be structurally competent.	Not suitable for high-clay or very high-grade ores where locking up valuable gold for years is not economical.

Process 2: CIL/CIP – The best choice for clayey or fine-grained disseminated gold ores?

This is the high-tech, high-efficiency workhorse of the industry. When the ore is too clayey or the gold is too fine for heap leaching, this is often the answer.

Yes, the Carbon-in-Leach (CIL gold processing) and Carbon-in-Pulp (CIP process) are the best methods for clay-rich or fine-grained ores. By grinding the ore into a slurry, they completely bypass the permeability issues that plague heap leaching.

This method is about total control, but that control comes at a price.

CIL/CIP: Key Considerations

Aspect	Description	Operational Insight
The Process	Ore is ground into a fine pulp and flows through agitated leaching tanks. Cyanide dissolves the gold, and activated carbon is added to adsorb the dissolved gold directly from the pulp.	It must be operated with the precision of a chemical plant, requiring constant process control of pH, cyanide, and dissolved oxygen. It is complex but highly efficient.
Critical Failure Point	“Preg-Robbing” Ore. Natural carbon in the ore can “rob” dissolved gold from the solution before your activated carbon can.	CIL is the direct solution to this. By having activated carbon present during leaching, the dissolved gold will preferentially adsorb onto the highly active added carbon. This is the main difference from CIP, where leaching happens first.
Best For	Higher-grade ores (>1.5 g/t) and ores with high clay content or preg-robbing characteristics. It offers the highest recoveries (90-97%) and is very fast (hours, not months).	Highest capital and operating cost due to the power-hungry grinding circuit and complex desorption electrolysis system.

Process 3: Gravity Separation – When should it be the first choice for gold recovery?

This is about getting the “easy” money first. It is the oldest gold beneficiation process in the world, and it is still incredibly relevant.

Gravity separation for gold should be a priority whenever an ore contains even a small amount of coarse, free gold. It is not a complete process on its own but a critical, low-cost first step before leaching to recover gold that cyanide would miss.

Ignoring gravity gold is one of the most common and costly mistakes in plant design.

Gravity Separation: Key Considerations

Aspect	Description	Operational Insight
The Process	Uses the high density of gold to separate it from lighter waste rock. Modern plants use centrifugal concentrators, jig separators, or shaking tables, often placed within the grinding circuit.	The return on investment for a gravity circuit is extremely high. A single coarse gold nugget can take days to dissolve in cyanide and would be lost to tailings in a 24-hour CIL circuit. Gravity recovers it instantly.
Critical Failure Point	The Nugget Effect. Relying solely on cyanide for an ore with coarse gold results in low recovery. The cyanide simply does not have enough time to dissolve large particles.	By removing coarse gold upfront with a gravity circuit, you improve the financial stability of the operation. Even if the leach plant has problems, you are still producing a high-value gravity concentrate every day. The payback period is often short.
Best For	Almost any oxidized ore. The presence of even 10-20% gravity-recoverable gold makes this addition highly profitable.	Not a standalone solution for ores where gold is exclusively microscopic.

Process 4: Combination Processes – How to handle complex oxidized gold ores?

Real-world ores are rarely simple. They are often messy, with a mix of different characteristics. The most profitable solution is often a hybrid approach.

Complex oxidized ores are best treated with a combination of processes. A common and highly effective strategy is to use a gravity circuit to recover coarse gold, followed by a CIL circuit to leach the fine gold from the gravity tailings.

This approach allows you to optimize the recovery for each type of gold present in your ore.

Designing a Hybrid Flowsheet

• Gravity + CIL: The gold standard for ores with both coarse and fine gold. It maximizes overall gold recovery rate by using the right tool for each job.
• Gravity + Heap Leach: For low-grade ores with some coarse gold. You pull out the high-value nuggets with a gravity circuit and send the low-grade tailings to a heap leach. This improves cash flow and overall project economics.
• Flotation + CIL: Sometimes, gold is associated with sulfide minerals even in an oxidized ore. A flotation step can be used to pull out these sulfides for separate, more intensive treatment, while the flotation tailings go to a standard CIL circuit. This is a common approach for refractory gold ore.

How do you choose the right gold extraction process based on ore characteristics and budget?

This is where metallurgy meets economics. The technically “best” process might not be the most profitable one for your specific situation.

The choice is a balance between your ore’s properties (grade, clay, particle size) and your financial constraints (capital cost vs. operating cost). Low-grade ore and a low budget demand heap leaching. High-grade ore and available capital favor the high recovery of a CIL plant.

Your gold mine feasibility study will analyze these trade-offs.

The Decision Matrix

Factor	Heap Leaching	CIL / CIP	Gravity Circuit
Ore Grade	Low (<1.5 g/t)	High (>1.5 g/t)	Applicable to all grades
Clay Content	Very sensitive; requires agglomeration	Not sensitive	Not sensitive
Capital Cost	Low	High	Very Low
Operating Cost	Low	High	Very Low
Recovery Rate	Low (50-75%)	High (90-97%)	Varies (5-50%)
Processing Time	Months / Years	Hours	Instant

How can you get a customized process flowsheet and equipment configuration for your ore?

A generic solution is a recipe for failure. Your mine is unique, and your gold ore processing equipment must be selected and sized specifically for your ore.

We provide a complete mineral processing EPC solution that starts with your ore. Send us a representative sample, and our metallurgical lab will conduct a thorough analysis. Our engineers will then design a custom-fit process flowsheet and provide a detailed equipment configuration and quote at no charge.

This is the only way to ensure your investment is sound and your plant is designed for maximum profitability from day one.

Conclusion

Choosing the right gold extraction process for oxidized ore is a critical decision. It requires a deep understanding of your ore’s personality and a realistic view of your budget. Start with the science, test your ore thoroughly, and you will build a plant that is profitable for years to come.