XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1497
of bulk sorting, it can also be trucked to different destina-
tions.) This is the last opportunity before the plant applies
significant amount of power and water to process the mate-
rial. SRK Consulting has been working in the area of pre-
concentration assessment for the past few years and offers
an independent viewpoint on economic options for Grade
Engineering ® (CRC ORE, 2022) As shown in Figure 1,
pre-concentration after blasting or primary crushing can
involve any combination of screening, bulk sorting and/or
particle sorting.
In the case of particle sorting, screening is typically
included in the flowsheet due to constraints required for
ejection system designs and equipment capacities. The
authors’ original interest in this field was how material may
preferentially break after crushing and whether this resulted
in grade deportment to certain size fractions. This led to
the development of a test protocol that later included sen-
sor evaluation of the coarse fraction, as grade deportment
alone was commonly not selective enough to generate a
true waste fraction.
SRK METHODOLOGY TO ASSESS PRE-
CONCENTRATION
SRK Consulting has developed a multi-stage methodology
to assess pre-concentration, targeted mainly at early stage
studies or projects. It is the authors’ opinion that opportu-
nities for pre-concentration (i.e., waste rejection, marginal
ore upgrading, impurity reduction) should be considered
by most early stage studies. This does not suggest that pre-
concentration will always be beneficial more likely this will
only be true in a minority of cases. However, it should still
be investigated and the SRK method strives to be as least
disruptive as possible: utilising drillcore assays, small mass
samples and low-cost testing methods performed by a fully
independent laboratory. In fact, samples that are being sent
for metallurgical testwork can also be used to evaluate pre-
concentration, before the material is crushed and prepared
for grinding and separation tests by which point any infor-
mation on preferential breakage is lost.
SRK’s methodology follows three stages: heterogene-
ity analysis, small sample laboratory testing and economic
evaluation encompassing a range of processing scenarios.
The method can be supported by Qualified (or Competent)
Persons authoring technical reports associated with scop-
ing, prefeasibility and feasibility studies.
Heterogeneity Analysis
SRK has developed two methods to quantify heterogeneity
based on drillcore interval assays (and at times, core scan-
ning results): 1) heterogeneity and scale and 2) composite-
sample relationship. Both methods have been described
previously by co-author Bob McCarthy (McCarthy, 2019),
with estimates of ore in waste (O/W) proportions and
waste in ore (W/O) proportions being one of the outcomes
of these analyses (see Figure 2). By following a consistent
evaluation method (and lab testing protocol), deposits can
be compared, benchmarked with others and results used to
gauge the likelihood of success. As shown in Figure 2, the
four gold projects have a wide range of W/O values that
increase over vertical distance for example, open pit bench
height or underground stope size.
Source: SRK 2024
Figure 1. Different forms of pre-concentration process (material is coarse, dry &conveyable)
of bulk sorting, it can also be trucked to different destina-
tions.) This is the last opportunity before the plant applies
significant amount of power and water to process the mate-
rial. SRK Consulting has been working in the area of pre-
concentration assessment for the past few years and offers
an independent viewpoint on economic options for Grade
Engineering ® (CRC ORE, 2022) As shown in Figure 1,
pre-concentration after blasting or primary crushing can
involve any combination of screening, bulk sorting and/or
particle sorting.
In the case of particle sorting, screening is typically
included in the flowsheet due to constraints required for
ejection system designs and equipment capacities. The
authors’ original interest in this field was how material may
preferentially break after crushing and whether this resulted
in grade deportment to certain size fractions. This led to
the development of a test protocol that later included sen-
sor evaluation of the coarse fraction, as grade deportment
alone was commonly not selective enough to generate a
true waste fraction.
SRK METHODOLOGY TO ASSESS PRE-
CONCENTRATION
SRK Consulting has developed a multi-stage methodology
to assess pre-concentration, targeted mainly at early stage
studies or projects. It is the authors’ opinion that opportu-
nities for pre-concentration (i.e., waste rejection, marginal
ore upgrading, impurity reduction) should be considered
by most early stage studies. This does not suggest that pre-
concentration will always be beneficial more likely this will
only be true in a minority of cases. However, it should still
be investigated and the SRK method strives to be as least
disruptive as possible: utilising drillcore assays, small mass
samples and low-cost testing methods performed by a fully
independent laboratory. In fact, samples that are being sent
for metallurgical testwork can also be used to evaluate pre-
concentration, before the material is crushed and prepared
for grinding and separation tests by which point any infor-
mation on preferential breakage is lost.
SRK’s methodology follows three stages: heterogene-
ity analysis, small sample laboratory testing and economic
evaluation encompassing a range of processing scenarios.
The method can be supported by Qualified (or Competent)
Persons authoring technical reports associated with scop-
ing, prefeasibility and feasibility studies.
Heterogeneity Analysis
SRK has developed two methods to quantify heterogeneity
based on drillcore interval assays (and at times, core scan-
ning results): 1) heterogeneity and scale and 2) composite-
sample relationship. Both methods have been described
previously by co-author Bob McCarthy (McCarthy, 2019),
with estimates of ore in waste (O/W) proportions and
waste in ore (W/O) proportions being one of the outcomes
of these analyses (see Figure 2). By following a consistent
evaluation method (and lab testing protocol), deposits can
be compared, benchmarked with others and results used to
gauge the likelihood of success. As shown in Figure 2, the
four gold projects have a wide range of W/O values that
increase over vertical distance for example, open pit bench
height or underground stope size.
Source: SRK 2024
Figure 1. Different forms of pre-concentration process (material is coarse, dry &conveyable)