Artisanal and Small-scale Gold Mining (ASGM) in Tanzania

posted by Eduard Cornew

Learn about the state of Artisanal and Small-scale Gold Mining (ASGM) in Tanzania and efforts to reform the sector.

Industrial Organization

There are approximately 1.5 million people directly involved in Tanzania’s Artisanal and Small-scale Gold Mining (ASGM) sector. Tanzania first legalized ASGM in 1995 after recognizing the sector’s poverty-alleviating effect on rural populations. Government regulation requires that miners obtain a Primary Mining License (PML) to work their land or employ others to do the same.

The mine site resembles a feudal economy. The License holders collect ~30% of the ore produced. Pit Managers, charged with coordinating labor around a single shaft, receive ~30% of production. The miners divide the remaining material among themselves.

Despite recent policy reform and widespread efforts to formalize the sector, many ASGM sites still operate without regard for regulation. Often referred to as “Clandestine Artisanal Miners,” many of those working in the industry live nomadic lives, moving from gold rush to gold rush in search of unexploited reserves.



ASGMs use shaft mining to excavate their ore, digging narrow tunnels along gold-rich quartz veins that extend as deep as 50 meters into the earth’s crust. Shafts are dug primarily using hand tools, sometimes with the aid of explosives.

Shaft mining is employed by ASGM’s as a cost-effective way of exploiting shallow high-grade deposits. Large Scale Mining (LSM) corporations with access to industrial equipment do not need to mine in this way. Instead, they use “clear-open pit” excavation techniques designed to exploit more sizeable and comparatively low-grade deposits. ASGM’s target ore with between 5 and 20 grams of gold per ton. A large scale mine is often economic at above 1.5 grams per ton.

We chose the name “Mwamba”- Swahili for “rock”- as a testament to the excavation method employed by Tanzanian ASGMs.  Mwamba is the Tanzanian equivalent of  “Eureka.” When a miner is prospecting and locates a quartz vein, it is common to hear them shout a celebratory “Mwamba” to announce the discovery of their next dig.



Once gold-rich ore is excavated, it needs to be crushed into a fine powder before it can be processed. The initial crushing is done by hand with makeshift hammers, almost exclusively by women. Ball mills- tumblers full of steel balls- complete the final stage of crushing, producing finely ground ore-powder. Ball mills are an indispensable piece of machinery reliably found on every ASGM site.


Gravity Separation

ASGMs use sluices to separate extraneous earth material from powdered ore and produce gold “concentrate.” They do this by running powdered-ore and water slurry down angled slides, allowing the heavy gold to lodge itself in rugs placed on the surface of the slide. The lighter material which does not embed itself in the mats referred to as “tailings,” retains ~60% of the ore’s gold. Miners pile these tailings by the ton on the periphery of their mines. Expensive Cyanide-In-Pulp processing infrastructure is needed to capture the gold that gravity separation methods leave behind.


Mercury Processing

After gravity separation is complete, miners conduct mercury processing, manually mixing the resulting ore “concentrate” with liquid mercury. When the mercury comes into contact with gold, it behaves like a liquid sponge, forming a gold-mercury amalgam referred to as “uncooked gold.” Miners place the uncooked gold on a coal fire, typically inside of a bottle cap, to burn off as much excess mercury as they can. The toxic fumes released during this reduction process are an extreme health hazard. Lazy eyes and motor dysfunction are a telltale sign of mercury toxicity commonly seen in ASGM communities. These symptoms are especially common in women, who are typically in charge of the mercury processing



Miners go to market with “uncooked gold.” Local Broker/Dealers purchase the uncooked gold, using borax and an oxyacetylene torch to expel the remaining mercury. This process yields an 18-22 karat gold dore that is entirely mercury-free, making it impossible to identify gold produced with mercury once it enters the market place. The Broker/Dealers who purchase uncooked gold are often the same individuals who supply artisanal miners with the mercury needed to produce it. The majority of ASGM derived gold is sold and refined in this manner.


ASGM Formalization in Tanzania

Tanzania is a party to the Minamata Convention on Mercury and is working with the United Nations to formalize its burgeoning ASGM economy. This collaboration has produced regulatory reform designed to help ASGMs access finance and adopt cleaner and more efficient practices and technologies.

Private sector intervention is needed to empower small-scale mining policy to realize its objectives.

Businesses that invest in the unmet needs of ASGM’s incentivize regulatory participation and reward compliance. Tanzanian ASGM remains largely untouched by modern mining and information technologies. Enterprises that steward responsible invest in ASGM and create access to technology stand to unlock tremendous value in the sector.

Eduard Cornew

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