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| Mechanize Small Scale Mining
Artisanal and small scale
gold mining (ASSM) offers lucrative employment opportunities to the locals of
most developing countries. The major drawback of ASSM is its impacts on the
environment as a result of improper mining and processing techniques. Exposed
and disturbed lands are usually subject to soil erosion and avalanches of
debris in active ASSM areas. Mercury is commonly used to concentrate gold, and
if not handled properly causes pollution of life supporting river systems.
Small
scale gold miners in many developing countries rely primarily on deposits
containing free gold and may be classified as shallow/deep alluvial or lode
type. The mining method used in artisan small scale gold mining employ very
basic technology. Shallow alluvial deposits are commonly found in valleys and
streams at depths not more than two meters. Deep alluvial deposits are found
along major riverbanks and older river courses, and usually at depths exceeding
six metres along the banks of rivers. The lode type of gold deposits is usually
composed of partially weathered gold bearing reefs, which are either outcrops
or near surface deposits. In Papua New Guinea, active artisanal mining are
commonly found abandoned mining areas like Panguna and Missima and also near
operating mines like Porgera, Eddie Creek in Wau Bulolo, Morobe Province. Not
only that but also other parts of the Provinces also have active small scale
miners. Other provinces include but not limited to: East Sepik, Sandaun, Enga,
Western, Eastern Highlands, Jiwaka, Madang, Western Highlands, Oro, Milne
Bay,Morobe.
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The small scale gold fields are mainly
riverine deposits where mining occurs along river banks, terraces and in active
river channels. Using poorly constructed sluice boxes, gold bearing material is
fed into the inclined sluice boxes. The box is constructed using plywood or
flattened roofing iron with wooden/metal ripples. These types of operations are
associated with low to very low recovery because of uncontrollable river flow
rates, incorrect inclination of the sluice boxes and inappropriate amounts of
feed material at any one time. It is extremely difficult to introduce
mechanised alluvial mining because of low skills and knowledge, isolation from
transport infrastructure and lack of basic infrastructure.
The
gold bearing gravels are concentrated by rippled sluice boxes. The fine gold is
not commonly trapped in the ripple compartments. The fine particles of sand
with gold in it are than poured into the panning dish for further panning. Mercury
is placed in into the panning dish to concentrate the fine gold particles.
Amalgamation is an efficient mean of extracting gold particles from
concentrates after panning or sluicing.
Health
and environmental impacts (Watch Video)
The
artisanal and small scale gold mining provides employment at local and national
levels, and the sector is an important source for the inflow of foreign
exchange into rural communities. However, small scale mining activities are
associated with sensitive health and environmental issues.
The
process of recovering gold by retorting and heating the amalgam over an open
fire is a dangerous practice. The open fire could be in houses or at river
banks and thus a whole family could be exposed to poisonous mercury fumes.
Concentrate from
sluicing near streams is usually mixed with mercury and a considerable amount
of mercury is lost to the streams. Apart from direct inhaling of mercury fumes
by miners, aquatic life also feeds on mercury lost into the river, which are
then eaten by the locals through the food chain. The Watut and Bulolo Rivers
has been subject to prolonged mercury contamination and discharges of
hydrocarbon wastes. The Watut people depend on the river for fishing, washing
and farming on the river banks.
Some miners in old
shafts and adits and they are consequently exposed to the trapped noxious gases
such H2S. Locals have been reported that they are buried alive when they burrow
through soft oxidized lodes or vein systems.
Some operators
locate their sluice boxes in streams, thus polluting the water. Silting and
stream discolouration are very common. Farmlands are usually destroyed by
mining activities. Locals even uproot big trees along structurally defined thin
gold deposits. Sometimes, the narrow gullies are not rehabilitated and are left
to be taken care of by nature.
Exposed and
disturbed lands are subject to soil creep widening the flow channels, and
debris avalanches are common along rivers at the active mining areas. The loss
of fertile land due to small scale mining puts socio-economic pressure on the
local society. Old gravel pits are usually abandoned without reafforestation.
Pits filled with stagnant water are common.
Education and training
Small-scale
mining technology in most developing countries is simple and attracts many
unskilled people. The desire for economic and social survival has attracted
many people to the industry. The law expects the licensed small-scale miner to
mine using effective and efficient methods, and observe good mining practices,
health and safety and protect the environment.
The Small Scale
Mining Branch of PNG Mineral Resources Authority (Formerly Department of
Mining) in Wau, Morobe Provine has created education and training materials for
the miners. The Department has produced seven booklets and DVDs on
•
Simple Gold Mining;
• Basic Mining Practice;
• Advanced Mining practice;
• Handling of Mercury;
• Occupational Health and Safety;
• Environmental Issues; and
• Economics of Mining.
The major focus
of the training resources is to ensure that small scale operations are safe,
environmentally friendly and economically viable.
Small-scale
mining operations in most developing countries have serious negative environmental
impacts. One of the major factors is the implementation of the associated
mining Acts which are lacking.
Donor agencies
like the World Bank, European Union and Japanese International Cooperation Agency
(JICA) have in recent times shown keen interest in the negative and positive
impacts of the PNG’s ASSM sector. AusAid and the World Bank have sponsored the
building of the ASSM sector capability in PNG through legislative framework and
training and awareness on the use of mercury.
Note: This article is a reproduction of a learning material with inclusion of up to date information.
Reference
[1] Ail, K. K. (2005. Kwoe River
Alluvial Gold Deposit Evaluation and Development Plan, PNG University of
Technology, Lae.
