Glycine — the simplest amino acid, better known as a food and pharmaceutical ingredient — has become one of the most talked-about reagents in gold mining. Glycine leaching offers a low-toxicity alternative to cyanidation, and it is gaining traction in Africa, Mongolia, Australia and beyond for treating difficult ores. This article explains how glycine works in gold extraction, where it is applied in mining, and why buyers should watch this market.
1. Why Is Glycine Used in Mining?
Traditional gold extraction uses cyanide to dissolve gold from ore. Cyanide is effective and cheap, but it is highly toxic — a single accident can devastate a watercourse, and regulators worldwide are tightening controls. The mining industry is actively looking for less hazardous lixiviants, and glycine has emerged as the leading candidate because it is:
- Low toxicity: glycine is a naturally occurring amino acid, biodegradable and safe to handle.
- Effective on difficult ores: carbonaceous (preg-robbing), high-copper and high-sulfur ores that respond poorly to cyanidation can often be leached with glycine.
- Recyclable: the glycine in the leach solution can be recovered and reused, cutting reagent cost and environmental load.
2. The Chemistry: How Glycine Leaches Gold
Gold does not dissolve in plain alkaline glycine solution. The leaching chemistry requires three components working together:
- Glycine: acts as a complexing ligand that binds gold into a stable water-soluble complex — a gold-glycine complex such as the bis(glycinato)aurate ion.
- Alkaline pH: the leach operates at high pH (typically pH 10-11), where the glycine is deprotonated and the gold complex is stable.
- Oxidant: an oxidizing agent (oxygen/air, hydrogen peroxide, or a copper-ion catalyst system) is required to oxidize the metallic gold so it can be complexed.
The overall process dissolves metallic gold from the ore into solution as the gold-glycine complex, which is then recovered (e.g. by carbon adsorption or precipitation). In the GlyCat™-type processes developed by industry (Mining and Process Solutions, Australia), a small amount of cyanide or another catalyst is used to accelerate the reaction, with glycine as the main lixiviant.
3. Glycine Leaching vs Cyanidation
| Aspect | Cyanidation | Glycine leaching |
|---|---|---|
| Toxicity | High (HCN risk) | Low (biodegradable amino acid) |
| Leach rate | Fast | Slower (improved with catalysts) |
| Preg-robbing ores (carbonaceous) | Poor | Better |
| High-copper ores | High cyanide consumption | Lower reagent consumption |
| Environmental footprint | High risk | Much lower |
| Maturity | Century-old standard | Growing industrial adoption |
Glycine leaching is not a universal replacement for cyanidation — for simple, free-milling ores cyanide remains cheaper and faster. The sweet spot is difficult ores and projects where cyanide is restricted or where environmental permitting makes cyanide unacceptable.
4. Where It Is Being Applied
4.1 Africa
Several African gold projects — including in West and Southern Africa — have evaluated or adopted glycine-based leaching, attracted by lower toxicity, simpler permitting and the ability to treat carbonaceous ores. South Africa’s mining research institutions have been prominent in glycine-leach development.
4.2 Mongolia
Mongolian gold operations, facing both harsh operating conditions and tightening environmental regulation, are among the markets where glycine leaching is being assessed for both new projects and tailings retreatment.
4.3 Australia
Western Australia is the development heartland of glycine leaching, with several projects advancing through pilot and early production stages.
4.4 Other applications
Beyond gold, glycine systems are being studied for leaching copper, nickel, cobalt and mixed oxide-sulfide ores, and for treating historic tailings.
5. What Mining Buyers Should Know
- Grade matters: mining uses technical-grade glycine at industrial scale; purity and heavy-metal content should be verified on the COA.
- Consumption can be high: glycine is consumed and partially lost in the leach circuit; total reagent cost depends on recovery efficiency.
- Supply reliability: as demand grows, secure, consistent supply of technical-grade glycine is becoming a procurement consideration for mine operators.
- Confirm the process: glycine leaching is a specialized metallurgy — work with process specialists and test on your ore before scaling.
6. FAQ
Is glycine leaching a real industrial process?
Yes — glycine-based leaching (including GlyCat-type processes) has advanced to industrial pilot and early production stage in Australia, with evaluation projects across Africa and Mongolia. It is a growing, commercially relevant technology.
Is glycine leaching a complete replacement for cyanide?
Not yet for all ores. It excels on difficult ores (carbonaceous, high-copper) and in low-toxicity projects, but free-milling simple ores are still usually cheaper to treat with cyanide.
What makes glycine leach more environmentally friendly?
Glycine is a biodegradable amino acid with low toxicity, so the risk profile of spills, tailings and water discharge is far lower than with cyanide.
What grade of glycine do mines use?
Technical/industrial grade glycine, typically supplied in bulk (bags, FIBC or bulk) — verify purity, moisture and heavy metals on the COA.
7. References and Further Reading
- Peer-reviewed literature on glycine and glycine-cyanide gold leaching (mineral processing journals)
- Industry technical literature on GlyCat-type processes and cyanide-free leaching
- Mining industry press on glycine leaching trials in Africa, Mongolia and Australia
This article is published for industrial and technical reference by PolyblueChem. Process details are typical industry knowledge; always validate against your ore and process specialists.
PolyblueChem supplies glycine (CAS 56-40-6) in food, pharmaceutical and technical/industrial grades with COA and MSDS. See our glycine guide for the full background. Contact us for specifications and quotations.