Mining Methods Vary Widely - Mining and the Environment: From Ore to Metal - page 247

FIGURE 5.12
Typical Distribution of High Grade
and Low Grade Ore Types

Ground Surface

Structural
Control-faults,
Fractures, etc While small-scale miners only mine

high grade zones, large-scale enter-
prises mine the high grade ores
together with low grade materials
which generally occur nearby.

Boundary of
High Grade Ore

Boundary of
Low Grade Ore
Mineralization

being offered at a low price, and the prospect of signii cantly reduced expenditure through
the recovery of mercury.
In addition to these health effects, gold rushes can cause serious social problems, par-
ticularly if a large inl ux of people takes place in an area occupied by a small population of
vulnerable, Indigenous People. Population pressure, environmental damage, crime, loss of
traditional resources, prostitution, alcohol, drugs, and the effects of HIV/AIDS can cause
a complete breakdown of traditional societies. Even in the absence of vulnerable groups,
gold rushes may cause a variety of social ills, and it could be argued that, in most cases, the
economic benei ts do not justify the social and environmental costs.
Another signii cant impact of much small-scale mining is the loss of mineral resources.
The low recovery rate has already been mentioned. Of even more concern is the 'high-
grading' involved in virtually all small-scale mining. While small-scale miners only mine
high grade zones, large-scale enterprises mine the high grade ores together with low grade
materials which generally occur nearby. This is illustrated in Figure 5.12 .
Removal of the high grade ore can reduce the overall grade to the extent that the
remaining resources are uneconomic to mine. Even where this is not the case, the presence
of numerous small excavations throughout the ore body can lead to instability and l ood-
ing of subsequent mining operations. It is therefore not surprising that many mining com-
panies deliberately avoid areas and situations where small-scale miners have been active or
are likely to appear in the event of a discovery.
In contrast to the impacts of gold rush mining, traditional small-scale mining may be
undertaken with minimal impact, as shown by the activities of the Kankana-ey people. The
underground mines of the Kankana-ey cause little surface disturbance and are relatively
safe compared to those in gold rush areas, because these highly skilled miners recognize
signs of instability and understand how to provide ground support. As the Kankana-ey live
close to their mines and have the expectation that they and their descendants will con-
tinue to do so, they have a vested interest in protecting their environment and maintaining
pleasant living conditions. Waste rock removed from underground workings is used for
construction of buildings, stairways, retaining walls, and terraces in the local villages. The
Kankana-ey do not use mercury, but manage to achieve gold recoveries of more than 80%,
using a range of traditional methods. Ores are, in fact, processed and reprocessed using a
variety of physical separation techniques, before being discarded. Similarly, water used in
processing is conserved and re-used by the community.

In contrast to the impacts of gold
rush mining, traditional small-
scale mining may be undertaken
with minimal impact