Mining in focus
The secret world of
gold processing
Various methods
have been employed
to process gold,
becoming more
labour- and technology
intensive, but also
more successful in
recovering, writes
independent consultant
Dr Nicolaas C.
Steenkamp, Bowline
Professional Services
MD Breton Scott, and
Leon Louw.
[18] MINING MIRROR APRIL 2018
W
hile there has been a
lot of talk in the
mining industry
about the mechanisation and
modernisation of mines, most
of these discussions focus on
the methods to extract the
rock material in which the ore
bodies are hosted, rather than
on the processing methods
after it has been unearthed.
Yet, the development of new
and innovative ways to liberate
gold from the rock material
is important and represents
the modernisation of an entire
mining process. Not only do these
processing methods need to be
more efficient and effective, but
it is imperative that they are also
environmentally friendly. Effective
processing of the ore plays a key
role in the viability of a project or,
at the end of the day, the profit
margins.
Types of gold ore
There are two types of gold
mineralisation: free gold and
refractory gold. Native gold or
free gold is exactly what the name
implies: it is not bound in any
other mineral that needs to be
removed and can be concentrated
by a combination of gravity
methods, such as leaching (for
example cyanidation) and/
or direct smelting. This type of
mineralisation is usually associated
with heavy mineral placer deposits,
such as alluvial gold deposits in
streams and rivers or quartz veins.
Therefore, most gold deposits
are found through gold panning
initially before locating the hard
rock source.
Refractory gold, on the other
hand, is bound with other
minerals, usually sulphides and
associated chalcophile elements.
This type of gold requires more