Environmental Engineering Reference
In-Depth Information
In many cases, further rei ning of the product also takes place on-site;
Mine waste management;
Mine closure and rehabilitation after exhaustion of the economic ore reserve and com-
pletion of rehabilitation;
Post closure mine management; and
Handover of land for other uses.
The primary processing of ore to produce a concentrated product is often included in mine
design, since it is the initial step of mineral processing or extractive metallurgy. Therefore,
the basic processes of separating metals from rock are discussed in this chapter. Chapter
Six discusses the two main subsequent principles of extractive metallurgy in more detail.
Generally the activities of most environmental signii cance are construction, ore and
waste rock extraction, mineral processing, and waste disposal. Dewatering is also a signii -
cant activity at some operations. Processing mining activities also have environmental
impacts but these tend to be less important. Rehabilitation and closure may have some
impact, but these activities are carried out with the objective of repairing any adverse
effects that may have occurred during mining, to leave a safe and stable mine site.
This chapter examines each stage of the mining and minerals life-cycle, identifying poten-
tial negative environmental effects and briel y describing actions taken to mitigate or prevent
them. Chapter Thirteen then details the main environmental issues. Environmental assess-
ment that is based on an appreciation and knowledge of mining will help to develop synergies
and to identify opportunities, avoiding additional costs and potentially creating new streams
of revenue, resulting in an improved performance both environmentally and economically.
4.1 IT ALL BEGINS IN THE EARTH
The ores which provide the substance of the mining industry are often complex compo-
sitions which require sophisticated understanding to locate, process, and utilize. A more
detailed discussion of the properties of metals and minerals for those who might wish to
review the basics is included in Chapter Eleven.
Types of Ores
As with arsenic, cadmium is a
by-product which is recovered in
smelters; no dedicated cadmium
or arsenic mine exists.
Ore may yield a single metal (simple ores) or several metals (complex ores) as shown in Table
4.1 . Ores that are generally exploited for only a single metal are those of iron, aluminium,
chromium, tin, mercury, manganese, tungsten, and some ores of copper. Gold ores may yield
only gold, but silver is commonly associated. Much gold, however, is extracted as a by-prod-
uct from other ores, predominantly copper. Ores that commonly yield two or three metals are
those of gold, silver, lead, zinc, nickel, cobalt, platinum, and manganese. Arsenic is commonly
associated with many gold deposits as well as copper and lead deposits, and in fact copper ores
are the primary sources of arsenic. Cadmium, which is often found in zinc-concentrate after
mineral processing, is usually removed at the smelter. Lead and copper ores may also contain
small amounts of cadmium (EIPPCB 2001). As with arsenic, cadmium is a by-product which
is recovered in smelters; no dedicated cadmium or arsenic mine exists, although artisanal
mining to extract arsenic compounds used as a cosmetic, has occurred in the Middle East.
The knowledge of primary and associated constituents in an ore body, is of prime
importance for the environmental assessment of a mine proposal. Fragmentation and
removal of rock materials and tailings expose rock surfaces that previously have been
 
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