In Zimbabwe, it is estimated that there are between 300,000 and 400,000 artisanal gold miners sustaining the livelihood of at least 2 million people. There are 200 registered “formal” large to medium-scale gold mines and thousands of small-scale gold operations producing, according to the official statistics, up to 5 tonnes of gold annually. This production from a large contingent of miners seems to be underestimated and most gold must be smuggled out of the country where prices are more attractive. About 20,000 to 30,000 people are directly involved in gold extraction in the Kadoma-Chakari region selected by the Global Mercury Project to implement demonstration units.
There are 3 categories of people in the artisanal gold mining operations in the region:
1. miners who excavate and extract semi-weathered gold ore and take this for processing at custom milling centers. There are about 3,000 to 5,000 people involved in this activity.
2. millers who work in the milling centers where the ore is milled and concentrated for the miners. There are probably about 1,000 to 2,000 people in 70 milling centers.
3. panners, individuals who concentrate alluvial gold by panning the gravels in creeks and rivers or re-processing tailings from former industrial mining operations. They represent the majority of individuals extracting gold. They are nomads and can represent a contingent of 15,000 to 25,000 people in the region.

Processing Methods Used
Ore extracted by miners is transported to the custom milling centers to be ground and concentrated by operators. The custom milling centers are a desirable solution as this organizes the activity and avoids the use of mercury in different places. However, the millers allow miners (customers) to use their own mercury at any step of the process. The technology employed by the custom milling centers varies. For crushing and grinding, some of them use wet stamp mills (3 or 5 stamps) with capacity of 0.2 to 0.5 tonne/h and some use jaw crushers followed by grinding with ball mills (capacity of 0.7 to 2 tonnes/h). For mineral concentration, the most popular methods are centrifuges and copper-amalgamation plates.
The centers charge between Z$ 10,000 (US$ 2.86)1 to Z$ 14,000 (US$ 4) per hour of grinding and concentration depending on the hardness of the ore. Using stamp mills, hard rocks take 5 hours/tonne to be ground and concentrated, whereas soft ores take 1.8 hours/tonne. Miners prefer milling centers with stamp mills, as they believe that ball mills retain part of the gold in the internal liners. The lack of gold liberation is an evident problem when using stamp mills and this is the main reason why miners recover less than 30% of the total gold by gravity separation followed by amalgamation. Stamp mills operate with water and the pulp is discharged through a 0.6
to 0.8 mm screen into a local-made centrifuge or on copper-amalgam plates.
The concentrates from the centrifuges are given to the miners and they perform their own amalgamation. The millers provide the miners with amalgamation barrels and they do not charge extra for this service. Miners can add whatever they want into the amalgamation barrels, including soap, acids, and sodium cyanide tablets. The material discharged from amalgamation barrels is concentrated by panning in a plastic bowl and the tailings pass through an amalgamating copper plate. Some miners take home the amalgamation tailings. They re-grind, sometimes add more 1 Auction rate: 1US$ = Z$ 3500; official rate is 1 US$ = Z$ 824 mercury, pan them at their backyards and roast them in kitchens. The fate of these Hgcontaminated amalgamation tailings is unknown.
It is common to see miners adding three teaspoons (150 g) of mercury in the centrifuges used for gravity concentration of gold. This “flours” part of the mercury that is lost with the tailings. The use of copper-amalgam plates is also very popular in the centers and to amalgamate the whole ore. The great majority of miners in the region do not use retorts as they claim that the process is timeconsuming as they use low-temperature bonfires. Instead they put the amalgam in a tin to be burned in a wood fire without any protection. The burning process is done either under supervision of a mlarge number of people or furtively in the bush. At low temperature, the retorting process is very
incomplete. Retorted gold beads with more than 20% of residual mercury are usual.
Most of the gold is left in the primary tailings and the millers apply vat-cyanidation to extract this remaining gold. Miners receive no compensation for the extra gold extracted by cyanidation. This is a source of conflict between miners and millers. Most milling centers have 5 to 10 cyanidation tanks to extract residual gold using vat-leaching but some millers have as many as 27 tanks. About 20 to 70 tonnes of tailings from the gravity circuit and from the amalgamation process are added to cement each tank to be leached with 18 kg NaCN/tank.
Panners in Kadoma-Chakari are isolated individuals either working in local rivers and streams, especially the Muzvezve River, or panning tailings from former mining company operations (sometimes with their authorization). Panners are from remote areas, some of them from neighboring countries and they are frequently harassed by local police while working in illegal areas. In the dry season, they divert the river and excavate the gravels to concentrate gold in improvised sluice boxes (known as James Tables). They process from 1.5 to 2 tonnes of material per day recovering 0.2 to 0.4 g Au and losing equal quantities of mercury (50g per 4 months). The amount of Hg lost in the milling centers is equivalent to the amount of gold being produced which is between 2 and 3 kg/month. When copper plates are used to amalgamate the whole ground ore, the miners estimate that they lose twice as much mercury. Assuming that all 70 milling centers in the region are losing between 2 and 4 kg of Hg /mo, something around 1.7 to 3.4 tonnes of Hg is being emitted to the environment in the Kadoma-Chakari region just from the milling operations. Considering the use of Hg by panners, the Hg losses in the region must be between 3 and 5 tonnes/a.