SEG - Society of Economic Geologists

22 SEG NEWSLETTER No 90 • JULY 2012
SEG NEWS
SEG GEOMETALLURGY FORUM
Geometallurgy – The Journey
A lot of what we do in our professional
careers is about project. Projects are
great. They have a start, a middle, and
an end. If things have gone as planned,
at the end of this process we have
achieved our goals—our targets—and
we can feel happy about a job well done.
Unfortunately, geometallurgy is not like
that. Geometallurgy is a journey or, as I
find myself telling people, “it is a commitment.”
Of course, the geometallurgical
journey can and will be broken into
steps or phases that resemble projects,
but overall, it is one long journey.
The key areas the geometallurgy journey
can be subdivided into are the technical
journey, the management journey,
and the business process journey. It is
worth looking at each of these, as they all
relate to the successful integration of geo -
metallurgy into the business of a mine.
THE TECHNICAL JOURNEY
One of the key deliverables from a
geometallurgical program is a forecast
of expected production output on some
time basis (such as quarterly, monthly,
or if you have been at geometallurgy
for a long time, weekly basis). The forecast
will be of key concentrator outputs,
such as mill throughput, mill primary
grind size, recovery of wanted metals,
and concentrate grade. This forecast
will be based on a model interacting on
the block model with expected feed
blocks for that time period. This model
then calculates the expected outputs
based on some independent variables
(such as head grade, mineralogical
make-up, grindability hardness index).
Having made a forecast, we want to
know how good our forecast was. Its
accuracy is calculated by a reconciliation.
We determine the actual throughput,
primary grind size, recoveries, and
concentrate grade for the target period
and compare it with our forecast (actually,
the reconciliation process is a lot
more complex a process than this, but
that is another discussion). We then
determine the error band between actual
results and forecast and decide if that
forecast was good, acceptable, or poor.
Then the process gets repeated. We
do another monthly or quarterly forecast
and reconciliation. Time and time
again we repeat this process because
stevewilliams@geomettech.com
this is essential and this is how we realize
the value in geometallurgy.
At some point in this repeating cycle
we will review our model and our
underlying assumptions in the forecast
(which could be the independent variables,
the domains, or the model itself).
These will be reviewed and if through
our journey to this point we have
learned new things or understood
things better, then we may enhance or
modify some of these components.
The models used to make these forecasts
would be expected to evolve and
perhaps be radically recast over the life
of a mine. Models designed in a mine
project’s prefeasibility or feasibility stage
of development are often simplistic as
they are used only to forecast annual
production for the feasibility study.
However, it is logical to use these models
or some enhancement of them at the
commencement of production. Equally,
it is logical to expect that these models
will be refined, enhanced, or changed
over time as more things are learned
about the fundamental geological drivers
for comminution and flotation or leaching.
It is a long way from an acceptable
error band on yearly forecasted production
to achieving the same error band
on monthly forecasted production.
Another area that evolves with time is
the delineation of the geometallurgical
domains. Geometallurgical domains are
those zones or areas that have commonality
in some aspects of metallurgical performance
(such as recovery and/or resultant
concentrate grade quality). The
domains are made to help us understand
a complex geological system by clumping
together these areas of similar types of
performance. It should also be pointed
out that there will be different geometallurgical
domains for comminution
and for mineral concentration (such as
flotation).
When a geometallurgy program be -
gins, it is impossible to know what and
where these geometallugical domains are
(because it requires that metallurgical
result feedback loop), so inevitably, initial
geometallurgical domains are built
up from the geological domains of the
deposit, but with the application of
some geometallurgical principles. The
geological domain approach is a good
starting place for geometallurgical do -
mains but in evitably the geo metallurgical
domains will
change or evolve
from there as we
carry on through
the mine life.
Typically,
STEVE WILLIAMS
(SEG 2010)
with porphyry copper-type deposits,
there are fewer geometallurgical
domains than geological domians. Some
geological domains have very similar
metallurgical performance. Eventually,
these domains will be clumped together
to form the geometallurgical domain.
However, for other geological entities,
this is not the case. For VMS-type de -
posits, the geological domains do not
well capture the flotation complexities of
these deposits. So, in this case, we may
see the evolution of more geometallurgical
domains than geological domains,
as we try to better describe the metallurgical
performance of that deposit.
It can thus be seen that the technical
world of geometallurgy is a journey,
with future learning leading to evolution
of models, domains, and key
assumptions that change with time.
THE MANAGEMENT JOURNEY
Geometallurgy crosses boundaries from
geology to mine planning to metallurgy.
It also touches on areas such as product
quality/marketing, projects, and exploration.
Given this breadth of reach of
geometallurgy, it means that geometallurgy
is a mine management theme.
Specifically, a mine that is implementing
a geometallurgy program cannot
just say that “this is a geology task or a
metallurgy task.” To do so would not
recognize the breadth and value of
geometallurgy and would inevitably
doom the program to probable failure.
There are a number of real management
issues relating to the successful
implementation of geometallurgy in a
mine or mine development project.
Some of the key issues include the following:
structure, reporting lines,
geometallurgy management, reports,
decision-making, communication, and
language. This list is large, with some
real challenges, and as with any of
these human issues, particularly as they
relate to change (change management),
these issues are not addressed once and
then resolved. This is a process or a
“commitment”! What is important is to