Mining Methods Vary Widely - Mining and the Environment: From Ore to Metal - page 223

nickel metal hydride rechargeable batteries for hybrid vehicles and portable electronic
devices); (3) small powerful magnets (neodymium used to make the magnets used in mini-
ature electric motors such as about 40 of these used in a typical automobile), and; (4) high
temperature corrosion resistant alloys (iridium used in surgical devices, thermocouples and
automotive emission catalysts).
China holds the leading position among producers of the rare Earth elements. Processing
of rare Earth concentrates, and partially processed or intermediate products, is carried out
at several locations in Europe, the USA and Japan, as well as in China. World production
of rare Earths is around 100,000 t/y rare Earth oxide (REO). Output of yttrium is signii -
cantly less (about 2,500 t/y yttrium oxide - Y 2 O 3 ). Global production data for scandium are
not easily publicly available (Spooner 2005).

Mercury
Mercury is one of the most interesting of all natural substances because it is the only metal
which occurs as a liquid at ordinary temperatures. It is also one of the easiest metals for
prospectors to recognize, since most mercury comes from the bright red mineral cinna-
bar. Traditionally mercury has been of great importance for its ability to combine with
gold, and hence to extract gold from placer or oxidized deposits by amalgamation. Until
recently, mercury was widely used in scientii c instruments such as thermometers and
barometers. However, new technologies have replaced most of these uses. Mercury is noto-
riously toxic, particularly in its organic compound methyl mercury. It readily volatilizes
and re-condenses so that, in an environment where mercury is present, the metal can be
absorbed by dermal contact or inhaled as vapour, or ingested on food. In the marine envi-
ronment it often bio-magnii es so that long-lived predators such as sharks and barracuda
may have relatively high concentrations of mercury in their tissue. Like gold, in its metal-
lic form it does not oxidize or react readily and, although it can be transformed into a less
problematic compound (mercury sulphide - the compound found in nature as cinnabar)
the chemical process is costly. This means that there is a 'global pool' of metallic mercury
circulating in the environment - between air, water, sediments, soil and living things.

There is a 'global pool' of
metallic mercury circulating in
the environment - between air,
water, sediments, soil and living
things.

Other minor metals
A number of metals are recovered often only as by-products of smelting or other min-
eral processing operations (Pearl 1974): arsenic (primarily a by-product of processing cop-
per ore), bismuth (a by-product of processing lead ore), cadmium (usually a by-product of
processing zinc ore), gallium (solely a by-product of bauxite - aluminium - or sphalerite -
zinc), or selenium (obtained in copper rei ning from electrolytic slime).

Non-metallic Ores - Industrial Minerals Mining

Mining is not restricted to extracting metals or fossil fuels such as coal. The industrial min-
ing industry comprises the wide range of mining operations to extract dimension stone;
sand and gravel; clay, ceramic, and refractory minerals; chemical and fertilizer minerals,
and other non-fuel, non-metallic minerals. Non-metallic ores also include rocks in which
gems such as diamonds are found. With the notable exception of gemstones and dia-
monds, non-metallic mineral resources are predominantly mined as a source of chemical
feedstocks or building materials. They are mined for a wide range of chemical and physi-
cal properties. Although metals such as gold or silver may be more glamorous, the value of
non-metallic minerals mined worldwide far exceeds that of metals ( Figure 5.1 ) .

Although metals such as gold or
silver may be more glamorous,
the value of non-metallic
minerals mined worldwide far
exceeds that of metals .