Artisanal Gold Mining Operations Research Articles

A responsible mining approach to the economic modeling of small-scale gold mining

Artisanal mining, known as “garimpo” in Brazil, is a legal activity predicted in the Brazilian mining code. However, society's concern over the sustainable development of the Amazon rainforest and media coverage of illegal gold extraction have had the effect of marginalizing and condemning the sector as a whole. Known in the international literature as small-scale and artisanal gold mining (ASGM), this sector involves millions of miners across the world and hundreds of thousands in Brazil, who make a living from it, feed their families, and foster local economies. However, ASGM miners use techniques and operating procedures that, if not controlled, mitigated and eventually replaced, could lead to significant social and environmental impacts. There are growing concerns over ASGM activities, and buyers, investors, and industrial sectors are willing to pay more for a product created in a responsible manner. However, questions remain as to how much the transition to a responsible operation would cost, and whether buyers would really be willing to pay for it. This research presents a proposal for the economic modeling of ASGM operations based on immersive work in three cooperatives of legal ASGM miners in Brazil. The proposed approach considers the SDGs (United Nations Sustainable Development Goals) of the 2030 agenda, as applied to small-scale mining, and the corresponding actions that are needed, based on a detailed survey of the costs of the analyzed operations, with the aim of guiding small-scale mining activities towards greater responsibility and sustainability. In the proposed model, the average profit obtained from mining operations is guaranteed and the size of the bonus reverts to the responsible areas surveyed. A financial analysis based on our responsible model, which was developed for the cash flow for a hypothetical operation over 10 years, yields an IRR of 54 % and a payback of 2.54 years, thus demonstrating its economic viability.

Groundwater characterization including prediction of the quality, fluoride, and nitrate occurrence in a typical artisanal mining area in Ghana: A hydrochemical and multivariate statistical approach

Groundwater quality has been compromised by both geogenic and anthropogenic activities. Also, the negative impact of the intake of groundwater with high fluoride and nitrate content has been well established. Artisanal gold mining operations within the Tinga-Maluwe areas go beyond a decade with no knowledge of the level of impact these activities have on the groundwater quality. Hence, this study aims to characterize the groundwater with emphasis on the quality for usage as well as the controls of fluoride and nitrate occurrence in the area using hydrochemistry and multivariate linear regression modeling techniques. This is to enhance groundwater monitoring and stakeholder decision-making processes in the catchment. The concentration order of the cations is Ca2+ > Na+ > Mg2+ > K+ and that of the anions is HCO3− > NO3− > Cl− > SO42− > CO32− > F− with a Na – Cl dominant water type. Apart from F−, NO3−, and TDS exceeding their acceptable limits in Tinga, the overall pollution, water quality, and percentage of pollution indices show that the groundwater is slightly to heavily polluted in Daklupe, Seripe, Tinga, Kablima, Maluwe, Sakpa, and Bekwa-kura communities. Mineral dissolution, especially carbonate minerals, is the dominant process controlling groundwater mineralization from the discriminant diagrams used, and the saturation indices. However, anthropogenic activities impact on the groundwater cannot be precluded from the MLRMs of OPI, WQI, and PPI. The MLRMs show that pH, SO42−, Na+, K+, Ca2+, and Mg2+ are the controls of F− occurrence while that of NO3− is by TDS and pH.

Investigation of techniques to replace amalgamation in artisanal gold mining operations

Artisanal gold mining is the leading source of anthropogenic mercury emissions worldwide. This article explores cost-effective gold leaching methods for skilled miners to address mercury's environmental and health impacts in this sector. A sample from Colombia's La Maria deposit, containing 48.87 ppm gold, ground to 80% below 0.13 mm, served as the basis for comparison. The standard whole ore amalgamation approach, commonly used by miners, resulted in less than 19% gold extraction. However, employing cyanidation with 1g/L of free cyanide extracted 84% of the gold within 24 hours. Among the unconventional processes investigated, using effluent from a local cassava processing plant as a lixiviant demonstrated promise. Two cassava varieties produced liquids with 267 and 600 mg/L of free cyanide, leading to 50.9% and 82.4% gold extraction from the ore in 24 hours, respectively. Another alternative method involved employing Dimethyl sulfoxide, a water-free reagent, as a gold-leaching lixiviant, resulting in a remarkable 96.5% gold extraction in just 2 hours. The researchers also modified the Merrill-Crowe cyanidation process by eliminating filtration and vacuum, instead utilizing bags filled with zinc (or aluminum) in the pulp. With reduced agitation to prevent aeration, over 99% of the gold precipitated on the zinc shavings within 2 hours. Furthermore, testing a hydrochloric solution (50%) with an oxidant demonstrated 83.9% and 100% gold extraction in 8 hours at ambient temperature and 50°C, respectively. It is crucial to note that successful implementation of these alternative strategies necessitates knowledge, investment, and customization to suit specific site conditions.

A Global Look at Mercury Exposures: Supporting the Goals of the Minamata Convention.

A Global Look at Mercury Exposures: Supporting the Goals of the Minamata Convention.

Nexus between Artisanal Gold Mining and Community Livelihood in Nandi and West Pokot Mining Regions, Kenya

Many studies on Artisanal Gold Mining (ASM) have estimated that it employs an estimated 13 Million people worldwide, with another 80 to 100 million people directly or indirectly benefiting. With the increasing rate of ASM operations in Nandi and West Pokot Counties, the extent to which AGM affects livelihood of people and the community and contributes to livelihood enhancement is not well-indicated in empirical literature. Therefore, the present study was conducted to determine the connection between ASM and community livelihood in Nandi and West Pokot Mining Regions, Kenya. The study employed a descriptive research design. Simple random sampling was used to select the respondents for interview. Primary data was obtained by using questionnaires, interview schedules and focus group discussions guide. Findings from the study indicated that majority (67%) of the respondents in West Pokot participated in artisanal gold mining activity all year round. Majority of the respondents in West Pokot County participated in mining activity on a full time basis while majority in Nandi County participate on a part time basis. Results further showed that 62 % of respondents in Nandi County were earning KShs. 4,001 and above from mining activities. Significant effect (p<0.05) of mining activities on incomes was recorded within the two Counties. Furthermore, significant relationship (p<0.05) between artisanal gold mining and socio economic activities within the mining communities was recorded. Therefore, it is recommended that stakeholders should recast mineral policy to ensure concurrent environmental sustainability and socioeconomic development.Keywords: Artisanal Gold Mining, Livelihood, Community

Characterization and risk of exposure to elements from artisanal gold mining operations in the Bolivian Andes

Artisanal and small-scale gold mining (ASGM) offers low-skilled workers an opportunity to elevate themselves out of poverty. However, this industry operates with little to no pollution controls and the cost to the environment and human health can be large. The objectives of this study were to measure levels of arsenic (As), manganese (Mn), cobalt (Co), lead (Pb), and mercury (Hg) in the environment and characterize health risks to miners and residents in an area with active ASGM operations. An exposure assessment was conducted at two different mining sites and a nearby village in the Bolivian Anders. The resulting measurements were then used to quantify cancerous and noncancerous health risks to children and adults working at and living near ASGM areas. Soil concentrations of As were well above background levels and showed great variations between the village and mining area. Mercury vapor levels at the two mining sites were approximately 30 times larger than the EPA reference concentration. The risk of developing non-cancerous health effects were primarily due to exposure to As and Hg. The probability of individuals developing cancer was considerably increased with adult miners having a probability of 1.3 out of 100. Cancer potential was driven by exposure to As, with de minimus cancer risk from all other elements. Based on the environmental characterization of elements in soils and Hg vapors, the risk of developing cancerous and non-cancerous health outcomes were above a level of concern based on EPA risk assessment guidance. Personal protective equipment was not worn by workers and Hg amalgam is commonly heated in workers’ homes. Better education of the risks of ASGM is needed as well as simple controls to reduce exposure.

Multiple methods for regional- to mine-scale targeting, Pataz gold field, northern Peru

Gold production in the Pataz district, northern Peru, is derived from mesothermal veins hosted by the Pataz batholith and basement-hosted epithermal and carbonate–base metal veins. At the regional scale, processing of Advanced Spaceborne Thermal Emission and Reflection Radiometer data can be used to delineate district-scale argillic alteration. One such area extends for tens of kilometres NNW of Vijus in the Maranon Valley. At the southern end of this area, basement-hosted quartz–carbonate–sulfide veins in faults support artisanal gold-mining operations. SEM analyses show that the alteration envelopes around these faults are dominated by illitic clays. These artisanal gold workings highlight the economic potential of the largely unexplored parts of the district-scale argillic alteration zone, further north. At the district scale, paleostress modelling maps areas of low minimum stress during Carboniferous ENE–WSW shortening, based on a new 1:25 000 geological map of the Pataz district. The resulting distribution of low minimum stress is used to predict sites of rock fracture under high fluid pressure, and consequent vein formation. These areas of low minimum stress occupy 11% of the modelled area but contain 50% of the known veins in the Pataz district. Some areas of low minimum stress contain no known veins, and where these are poorly explored or poorly exposed, they are proposed as potential targets for gold exploration. In combination with SEM microanalysis, ASD hyperspectral reflectance analysis of drill core samples shows that visible proximal sericitic alteration around batholith-hosted auriferous veins is predominantly phengitic illite. Automated software interpretation of ASD reflectance spectra using The Spectral Assistant shows that sericite in cryptic alteration distal from auriferous veins varies from mainly illite adjacent to the phengitic illite zone, to more distal muscovite. Reactivation of faults and mineralised vein contacts during the largely Cenozoic Andean orogeny produced chlorite alteration that locally overprints proximal phengitic illite alteration. ASD spectrometry identifies relict phengitic illite in some chloritic alteration zones and thus indicates proximity to mineralised veins at the deposit scale. Elevated pathfinder element concentrations within proximal phengitic illite alteration zones around batholith-hosted veins do not extend more than a few metres beyond the visible alteration envelope. The alkali alteration index [(Rb + Cs)/Th]N is elevated above background levels for up to 15 m beyond the visible sericite alteration zone in one of two holes investigated. In the other hole, both [(Rb + Cs)/Th]N and 3K/Al can be used as a lode-scale vector to gold-bearing veins within broad intersections of visible sericite alteration.

Cyanidation of mercury-rich tailings in artisanal and small-scale gold mining: identifying strategies to manage environmental risks in Southern Ecuador

In many countries, such as Brazil, Colombia, Ecuador, Indonesia, Venezuela and Zimbabwe, amalgamated tailings are leached with cyanide to recover remaining gold. This paper describes a recently completed study conducted at seven gold processing centers in Portovelo-Zaruma, Southern Ecuador, which involved consultation with local miners. The objective of the study was to understand the behaviour of mercury (with a focus on mercury loss) in artisanal gold mining operations through the evaluation of two cyanidation processes (Merrill-Crowe and Carbon-in-pulp), using a participatory approach. In order to assess the kinetics of mercury dissolution in cyanide, a bottle roll test was conducted in the laboratory. In the Merrill-Crowe cyanidation process, an average of 24.2% of metallic mercury was determined to be trapped at the bottom of the agitation tanks; 33.1% of mercury is lost in association with solid material and 11.7% is lost in solution. Approximately 31.0% of mercury in solution is sent to the zinc precipitation cells from which 27.8% is precipitated on the zinc shavings, with 3.23% remaining in solution. The mercury precipitated on to the zinc is lost to the atmosphere when the shavings are burned at 900 °C. In the Carbon-in-pulp (CIP) leaching system, 11.2% of the mercury is lost with the solid tailings; 31.6% of the mercury is associated with fine particles in suspension and 50.8% is likely dissolved. About 2.68% is trapped at the bottom of the tank and 3.72% is absorbed by the activated carbon. The bottle roll test revealed that mercury dissolution is directly proportional to cyanide concentration. At 10 g/ton of cyanide, approximately 42% of mercury was leached, whereas all gold was solubilized. During this study, miners recognized the risk associated with the cyanidation of mercury-rich tailings, and were aware of how much mercury is discharged to local streams and to the atmosphere. The active participation of miners in this study has led to the strengthening of their knowledge and awareness of mercury contamination, and has enhanced their understanding of the nature of the problem, as well as the weaknesses and strengths of the system they operate.

Abandoned artisanal gold mines in the Brazilian Amazon: A legacy of mercury pollution

The modern gold rush in the Brazilian Amazon attracted millions of people to become artisanal miners in order to escape complete social marginalization. The rudimentary nature of artisanal mining activities often generates a legacy of extensive environmental degradation,both during operations and well after mining activities have ceased. One of the most significant environmental impacts is derived from the use of mercury (Hg), which is illegal for use in gold amalgamation in Brazil, but continues to be the preferred method employed by artisanal gold miners. The general population is unaware of the capricious nature of mercury and artisanal mining activities. Moreover, individuals in positions of political or economic infiuence tend to be negatively biased towards artisanal mining and government policies do not effectively address the realities of these activities. Affected communities have consequently been ignored,and mistrust towards outside parties is high. Not surprisingly, miners are suspicious of and unlikely to employ externally derived solutions to reduce mercury emissions. This article reviews the use of mercury in artisanal mining and highlights the role miners, governments and non‐governmental organizations (NGOs) have played in communicating facts, perpetuating myths and deriving solutions for mercury pollution. This article also raises some key concerns that must be addressed to understand the behaviour of mercury in the environment and identifies solutions for problems facing communities where artisanal gold mining operations have been abandoned.