Mining Methods Vary Widely - Mining and the Environment: From Ore to Metal - page 245

tasks are performed more by women. The processing of gold is a woman's job. Processing
areas are located close to homes, facilitating integration of processing activities with child-
rearing and household tasks. The man or woman who owns a tunnel is the 'supplier'
who i nances the operations including providing food for the workers. One feature of the
Kankana-ey tradition is the sharing of ore and concentrate among community members.
Older women invariably receive priority in distribution of both ore and concentrate.
The Kankana-ey have also been involved in co-operative ventures with mining companies,
both as contract miners and as suppliers of tailings for re-treatment in Carbon-In-Pulp plants.

Environmental Impacts of Artisanal Mining

Clearly, with the wide range of techniques used by small-scale miners, resulting environ-
mental impacts are also variable in type, extent, and severity. The worst excesses of the gold
rushes cause the most severe adverse environmental effects with widespread surface dis-
turbance leading to accelerated erosion and sedimentation of local streams. Rainfall on the
typically 'pock-marked' surface creates numerous small pools which provide ideal breeding
sites for mosquitoes. The situation is usually aggravated by uncontrolled disposal of wastes
including sewage, which in the worst cases, leads to diseases such as typhoid and cholera.
The use of mercury introduces a range of other problems, some due to occupational
exposure, and others due to environmental contamination. Partly chemical and partly
physical, gold concentration by amalgamation takes advantage of the fact that free gold
particles amalgamate with mercury. Amalgamation consists of alloying mercury to
gold and silver. Gold in pyrite or other minerals cannot be recovered by amalgamation.
Today only a very few commercial gold production facilities use amalgamation, but the
use of mercury continues to be the preferred method in artisanal gold mining operations.
Mercury is cheap, and its application is simple. However, it is also environmentally dam-
aging, both to workers' health and the surrounding ecosystem. Aritisanal miners mix
i nely ground gold-bearing ore with mercury. Free gold particles amalgamate with mercury
and gold is separated by simply heating to evaporate the mercury. Two sources of mer-
cury release occur: (1) much mercury escapes in the often rudimentary heating/evapora-
tion process; (2) remaining mercury is discharged with tailings directly to the terrestrial or
aquatic environments ( Figure 5.11 ) .
Smelting of mercury amalgam to recover the contained gold and silver involves heating
to volatilize the mercury. While it is a relatively simple process to recover the volatilized
mercury by condensation, this seldom occurs. Where smelting takes place indoors with-
out any vapour extraction system, as in many small-scale mining situations, the mercury
condenses on interior surfaces such as ceilings, l oors, walls, and furnishings, where it is
indistinguishable from the general grime from other combustion deposits. Accordingly,
workers involved in gold recovery receive exposure by breathing mercury vapour, and by
dermal contact with contaminated surfaces. As discussed later, they may also be exposed to
mercury in drinking water and in food.
In terms of worker exposure, the situation is better where smelting operations take place
outdoors or in open-sided buildings, as was the case at Talawaan. However, in such cases,
the mercury vapour is more widely dispersed in the surrounding environment, condens-
ing on vegetation and the exteriors of buildings, from where it will be washed by rainfall
into the soils, and ultimately into the surface drainage system.
Another pathway for surface water contamination by mercury, concerns the disposal of
tailings and runoff from the grinding and smelting activities. Often, these wastes are dis-
charged to the nearest stream or river ( Figure 5.11 ) , which may be used by local people for

With the wide range of
techniques used by small-scale
miners, resulting environmental
impacts are also variable in type,
extent and severity.

Today only a very few
commercial gold production
facilities use amalgamation, but
the use of mercury continues
to be the preferred method in
artisanal gold mining operations.