PRECONCENTRATION
Sorting exploration projects
Ore sorting can be very important in determining
the economic value of a project. For example,
following completion of a large diameter
diamond core hole (MSDD261), a further
campaign of ore sorting is set to commence to
verify the positive results received from initial
test work on Middle Island Resources Ltd’s Two
Mile Hill tonalite deeps deposit at its 100%-
owned Sandstone gold project in Western
Australia.
n Precursor to first mineral resource for upper
half of the exploration target and potential
economic upgrade for project
n Previous scoping level test work indicated that
sorting can deliver a 185%-257% increase in
grade, with gold recoveries in excess of 93%
and 64% of the sorter feed material being
rejected
n The new more definitive, ore sorting campaign
will include iterations around crush size and
grade range, designed to enhance the original
results
n Validation would likely lead to a significant
positive impact on project economics,
delivering reduced haulage and process
operating costs, and lower tailings disposal
requirements.
Middle Island Managing Director, Rick Yeates,
said: “Ore sorting offers the potential to make a
significant positive impact on the economics of
the Two Mile Hill tonalite deeps deposit. Should
the new, more definitive, ore sorting campaign
replicate or improve on the initial trial results,
bulk underground mining at Two Mile Hill
becomes a very real opportunity that would
substantially extend and enhance the envisaged
project production schedule.
“While the focus of the current ore sorting
campaign is very much on the deeper
underground potential of the Two Mile Hill
deposit, given that material is available from
MSDD261 through the oxide profile, we will
utilise the opportunity to also assess the
response of the open-pit mineralisation to ore
sorting.”
A series of four primary (fresh) composites
have been selected from HQ and PQ diamond
core from MSDD261 for crushing prior to ore
sorting. The composites comprise broad, single,
continuous intervals of half core over three grade
ranges (high grade - HG, medium grade - MG and
low grade - LG). The high grade composite,
comprising solely half PQ core, will be separated
into two fractions for crushing to -45mm/+15mm
and -30mm/+10mm to assess the impact of crush
size on sorting, while the MG and LG composites
are derived from half HQ core and will be crushed
at -30mm/+10mm.
The composites will be provided to Steinert for
ore sorting at its commercial-scale unit in Perth.
36 International Mining | MAY 2018
The applied sensors will comprise a combination
of XRT (to detect and separate higher density
sulphides associated with gold) and laser (to
detect and isolate quartz, which hosts the vast
majority of gold).
While the priority remains on establishing the
sorting characteristics of the primary (fresh)
material, two (or possibly three) weathered/
oxidised composites of half PQ diamond core will
also be submitted for sorting at a -45/+15mm
crush size, in order to determine the validity of
applying ore sorting at the planned Two Mile Hill
open pit deposit. In this case iterations will focus
more on material type (oxidation state), rather
than grade range and crush size.
As with the primary (underground) component
of the deposit, a positive ore sorting outcome on
the oxide mineralisation has the potential to
reduce the unit haulage and process operating
costs, thereby increasing the size of the optimum
pit, resulting in additional potential open pit mill
feed.
NextOre, the company being formed by the
three partners, CSIRO and industry players
Advisian and RFC Ambrian, has developed an
advanced sensor system that takes advantage of
magnetic resonance technology. It illuminates
batches of ore with short pulses of radio waves,
assessing ore grade and enabling high tonnage
sorting at extremely high speeds.
NextOre’s ore sorter is able to detect the
magnetic resonance signatures of many
minerals, including the most common
economically significant iron-and copper-bearing
minerals. It also has t