Artisanal and small-scale gold mining — universally abbreviated ASGM — is the segment of the global gold industry characterised by individual miners, family groups, or small cooperatives working with limited mechanisation, modest capital investment, and techniques that have changed little in their essentials since antiquity. ASGM is simultaneously one of the most socially significant and environmentally consequential forms of mineral extraction on earth. It accounts for roughly 20 per cent of global gold supply and provides direct livelihoods to an estimated 15 million miners across more than 70 countries, with a further 100 million people dependent on the sector in support roles — figures documented by the United Nations Environment Programme (UNEP) and the World Bank in successive assessments. It is also, by a wide margin, the single largest source of anthropogenic mercury pollution worldwide, a distinction that has drawn it into the centre of international environmental diplomacy and, increasingly, into the supply-chain scrutiny of the jewellery industry.

Defining the Sector

The boundary between "artisanal" and "small-scale" mining is not universally standardised; national legislation defines thresholds differently. In practice, the combined term ASGM denotes operations that are labour-intensive rather than capital-intensive, that typically lack the formal permitting, environmental management plans, and occupational-health infrastructure of large industrial mines, and that often operate in legal grey zones — either in jurisdictions where formalisation pathways are absent or prohibitively complex, or in areas where customary land rights and formal mineral titles conflict. A significant proportion of ASGM production globally enters commerce through informal channels, making precise supply-chain tracing difficult.

ASGM should be distinguished from the broader category of artisanal and small-scale mining (ASM), which encompasses coloured gemstones, diamonds, tin, tungsten, tantalum, and other minerals. The gold subset is singled out in international policy because of the mercury problem: no other artisanal mineral commodity relies so heavily on a substance that is simultaneously a potent neurotoxin, a persistent environmental contaminant, and the subject of a binding multilateral treaty.

Mercury Amalgamation: The Core Process

The chemistry of mercury amalgamation is straightforward and has been exploited since at least Roman times. When liquid mercury is mixed with gold-bearing ore or alluvial concentrate, mercury selectively bonds with gold particles — including fine "flour gold" too small to recover by gravity separation alone — to form an amalgam, a silvery paste. The amalgam is then separated from the remaining material and heated, typically over an open flame, to volatilise the mercury and leave behind a sponge of raw gold. This retorting step is where the gravest environmental and health consequences arise.

In the absence of a closed retort — a sealed vessel that captures and condenses mercury vapour for reuse — the burning of amalgam releases elemental mercury directly into the air. Miners who heat amalgam in unventilated spaces, or who hold the amalgam over a flame by hand, receive acute inhalation exposures that can cause immediate neurological effects. Chronic low-level exposure, common in mining communities where amalgam burning is a daily occurrence, leads to the constellation of symptoms historically described as "mad hatter's disease": tremor, cognitive impairment, sensory disturbances, and, in severe cases, irreversible neurological damage. Children and pregnant women are disproportionately affected; methylmercury formed when elemental mercury enters aquatic systems bioaccumulates through food chains and reaches high concentrations in fish consumed by riverside communities far downstream of any mine site.

UNEP's Global Mercury Assessment has repeatedly identified ASGM as responsible for approximately 37–38 per cent of total global anthropogenic mercury emissions to the atmosphere — more than coal combustion, more than cement production, more than any other single human activity. The figure is not static: as ASGM has expanded in sub-Saharan Africa, Latin America, and parts of South and South-East Asia over the past two decades, absolute mercury releases have grown even as per-unit efficiencies have improved in some regions.

Geography and Scale

ASGM is most concentrated in three broad regions. In sub-Saharan Africa, major producing countries include the Democratic Republic of Congo, Mali, Burkina Faso, Ghana, Tanzania, and Zimbabwe; the sector here is often deeply intertwined with rural poverty, post-conflict economic recovery, and, in some cases, armed-group financing. In Latin America, Colombia, Peru, Bolivia, Brazil, and Venezuela host large ASGM populations; the Amazon basin has seen particular expansion, with associated deforestation and mercury contamination of river systems affecting indigenous communities. In Asia, Indonesia, the Philippines, Mongolia, and parts of Myanmar and Cambodia are significant producers.

In each region, the social profile of ASGM miners is broadly similar: predominantly male, often migrant, frequently operating without formal contracts or social protections, and motivated by the combination of gold's high value-to-weight ratio and the absence of alternative income sources. Gold's price sensitivity matters enormously — periods of elevated gold prices, such as the sustained bull market of 2008–2012 and the renewed highs of 2019–2024, reliably draw new entrants into ASGM, expanding the sector faster than regulatory capacity can respond.

The Minamata Convention

The Minamata Convention on Mercury, adopted in Kumamoto, Japan, in October 2013 and entering into force in August 2017, takes its name from the Japanese coastal city where, beginning in the 1950s, industrial discharge of methylmercury into Minamata Bay caused one of the most severe mass poisoning events in recorded history. The Convention is administered under UNEP and, as of 2024, has been ratified by more than 140 parties.

ASGM occupies a dedicated article — Article 7 — within the Convention text, reflecting the sector's centrality to the global mercury problem. The Convention does not prohibit mercury use in ASGM outright, a political accommodation of the reality that abrupt prohibition without viable alternatives would simply drive the practice underground while depriving millions of their livelihoods. Instead, it requires each party with "more than insignificant" ASGM activity to develop and implement a National Action Plan (NAP) that sets out measures to reduce and, where feasible, eliminate mercury use. NAPs are expected to address formalisation of the sector, introduction of mercury-free or mercury-reduced processing technologies, health and safety standards, and mechanisms for the sound management and disposal of mercury waste.

Progress under the Convention has been uneven. A number of countries — Peru, Colombia, Indonesia, the Philippines, and others — have submitted NAPs and established national programmes with varying degrees of implementation. Others have struggled with the administrative and financial demands of formalisation in contexts of weak governance. Independent assessments by UNEP and the Minamata Convention Secretariat have noted that while awareness has increased and some pilot programmes have demonstrated mercury-free alternatives at scale, overall mercury use in ASGM globally has not declined significantly in the decade since the Convention's adoption.

Mercury-Free Alternatives

The technical alternatives to mercury amalgamation are well-established; the barriers to adoption are primarily economic, logistical, and social rather than scientific. The principal alternatives include:

• Improved gravity concentration: Centrifugal concentrators (such as the Knelson or Falcon designs), shaking tables, and spiral concentrators can recover fine gold without mercury when properly operated and maintained. Capital costs are modest relative to industrial mining but significant for individual artisanal miners.
• Whole-ore amalgamation elimination: Many ASGM operators mix mercury with unprocessed ore, a practice that is particularly mercury-intensive and inefficient. Shifting to amalgamation only of pre-concentrated material — or eliminating amalgamation entirely in favour of gravity methods — can reduce mercury use by 80–90 per cent in suitable ore types.
• Closed retorts: Where amalgamation continues, closed retorts that capture mercury vapour and allow its condensation and reuse dramatically reduce atmospheric emissions and recover mercury for repeated use, lowering both health risk and input costs. Retort adoption has been a focus of numerous NGO and government programmes; uptake remains incomplete, partly because open-flame burning is faster and requires no equipment investment.
• Cyanide leaching: Cyanide-based processing is more efficient than mercury for many ore types and is the standard in industrial mining, but it introduces its own toxicological and regulatory challenges and requires more sophisticated management than most ASGM operators can sustain without external support.
• Borax smelting: The use of borax as a flux in direct smelting of gold concentrates — a technique documented and promoted by researchers including those associated with the Nordic Institute for Asian Studies — has shown promise in the Philippines and elsewhere as a mercury-free processing route accessible to small operators.

Formalisation and Supply-Chain Implications

The jewellery industry's relationship with ASGM gold is complex and largely invisible at the point of retail. Gold is a fungible commodity: once refined, ASGM gold is chemically indistinguishable from gold produced by large industrial mines, and the two streams commingle at refineries, bullion banks, and commodity exchanges. Responsible sourcing initiatives have attempted to address this opacity through chain-of-custody certification schemes. The Fairtrade and Fairmined standards — administered respectively by Fairtrade International and the Alliance for Responsible Mining — certify gold from organised ASGM groups that meet defined social, environmental, and mercury-reduction criteria, and command a price premium intended to support community development. The volume of certified ASGM gold reaching the market remains small relative to total ASGM production, but the standards have established a proof of concept for traceable, responsibly sourced artisanal gold.

The London Bullion Market Association's Responsible Gold Guidance and the OECD's Due Diligence Guidance for Responsible Supply Chains of Minerals from Conflict-Affected and High-Risk Areas both address ASGM as a risk category requiring enhanced due diligence by refiners and downstream purchasers. The practical effect has been to push large Swiss and other international refiners to implement more rigorous know-your-supplier programmes, though critics note that the complexity of ASGM supply chains — often involving multiple intermediary traders before ore or dore reaches a refinery — makes meaningful traceability difficult to achieve at scale.

Health, Environment, and Human Rights

The human cost of mercury exposure in ASGM communities is substantial and underreported. Occupational health surveillance in artisanal mining regions is sparse; many affected individuals never receive a diagnosis linking their symptoms to mercury exposure, and mortality attributable to chronic mercury poisoning is rarely captured in national health statistics. Studies conducted in ASGM regions of Ghana, Tanzania, the Philippines, Indonesia, and the Amazon basin have documented elevated blood and urine mercury levels in miners and their families, with neurological and renal effects detectable even in populations not directly involved in processing.

Beyond mercury, ASGM carries a range of other environmental and human-rights concerns: deforestation and habitat destruction in alluvial mining areas; cyanide spills; child labour (documented by the International Labour Organization as a persistent problem in parts of Africa and Asia); dangerous working conditions including tunnel collapse; and, in conflict-affected regions, the use of ASGM revenues to finance armed groups — the "conflict gold" problem that parallels the better-publicised conflict-diamond issue.

ASGM and the Gemstone World

For the coloured-gemstone trade, ASGM is a cognate and instructive case. Many artisanal gemstone miners work in conditions broadly similar to those of ASGM operators — informal, under-resourced, operating in legal grey zones, and largely invisible to end consumers. The mercury problem is specific to gold, but the structural issues of formalisation, fair pricing, health and safety, and supply-chain transparency are shared across artisanal mineral extraction. Initiatives developed for ASGM — certification schemes, community development premiums, due-diligence frameworks — have informed parallel efforts in the coloured-gemstone sector, including the Sustainable Gemstones Initiative and various mine-to-market traceability programmes. The Minamata Convention, in turn, has elevated international awareness of the broader governance deficit in artisanal mining, creating political space for regulatory reform that benefits gemstone miners as well as gold miners.

Outlook

The trajectory of ASGM over the coming decades will be shaped by the interaction of gold prices, population growth in producing regions, the pace of formalisation, and the effectiveness of mercury-reduction programmes under the Minamata Convention. UNEP and World Bank analyses suggest that demand for artisanal gold is unlikely to decline in absolute terms given demographic and economic pressures in producing countries; the policy challenge is therefore not elimination of ASGM but its transformation into a sector that provides livelihoods without poisoning the people who work in it or the ecosystems that surround it. That transformation is technically achievable — the alternatives to mercury are proven — but it requires sustained investment in governance, training, equipment access, and market linkages that has so far materialised only partially and unevenly.

Further Reading

• UNEP Global Mercury Assessment 2018, unep.org
• Minamata Convention on Mercury — Parties and Signatories, minamataconvention.org
• World Bank: Artisanal and Small-Scale Mining, worldbank.org
• OECD Due Diligence Guidance for Responsible Mineral Supply Chains, oecd.org