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Diamonds are the hardest natural mineral. Compared
with the second hardest mineral, corundum,
which can be used for grinding high-alloyed steels,
the abrasive hardness of diamonds is 140 times
higher. Hence diamonds can only be machined by
diamonds. To do so, diamond crystals with different
degrees of hardness are used.
Every year approximately 25 to 30 tonnes of the
precious raw material are extracted from mines all
over the world. The largest deposits are situated
in Russia, Australia, Canada and in the south of
Africa. Every so often, new deposits are found, although
the search for deposits that are worth
working has become increasingly difficult and
more cost-intensive. Estimates are that the exploration
costs of the entire sector amounted to about
800 million US$ in 2007. That is roughly three
times as much as the costs incurred in 2002.
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A raw diamond – the objective
of all efforts. |
Nevertheless only about one fifth of the worldwide
demand can be met with natural diamonds. Therefore
industry has been using synthetically produced
diamonds, which are less expensive, for a
number of years now.
However, natural diamonds are still preferred when
it comes to exclusive jewellery or inflation-proof investments.
The worldwide economic growth has
created an increased demand for the precious
mineral, especially in China and India, which are
experiencing an economic boom. Nevertheless,
the largest buyer of diamond jewellery is still the
USA, accounting for almost 50 % of the purchases.
Most deposits consist of diamonds that some 70
to 150 million years ago were ejected by eruptions
onto the surface of the earth with kimberlite, a volcanic
material. Hence they must first be extracted
from the matrix without being damaged.
In most diamond mines, this complex process is
nowadays handled by high-pressure grinding rolls,
and in many cases these are POLYCOM@ plants.
The ore-breaking process enables the careful extraction
of diamonds up to a diameter of 25 mm,
which equals to a gross weight of 150 carat. The
POLYCOM@ grinding rolls moreover produce a very
high proportion of fines, thus facilitating the
processes in the downstream plant sections, so
that operating and investment costs are significantly
cut down.
In August and in December, further POLYCOM@
grinding rolls went into operation in Canada, at
diamond mines in Snap Lake and in Ontario.
The POLYCOM@ is not only perfectly suitable for
breaking diamond ore, but it has also been a huge
success when it comes to processing other minerals.
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