WORLD PROSPECTS
Kirkland Lake’s Fosterville to benefit from Chrysos PhotonAssay
Kirkland Lake Gold is to install a Chrysos
PhotonAssay unit at its Fosterville mine, in
Victoria, Australia, as it looks to simplify, speed
up and improve its mineral assaying process.
The agreement with Chrysos has seen the unit
delivered to Fosterville, with the installation to be fully
operational by early October.
Originally developed at Australia’s national science
agency, CSIRO, PhotonAssay delivers faster, more
accurate gold analysis, Chrysos says, being a
quantitative, chemistry-free replacement for fire assay
on-site and in the laboratory.
“Hitting samples with high-energy X-rays, the
technology causes excitation of atomic nuclei allowing
enhanced analysis of gold, silver, and complementary
elements in as little as two minutes,” the company
says. “Importantly, Chrysos PhotonAssay allows large
samples of up to 500 g to be measured and provides a
true bulk reading independent of the chemical or
physical form of the sample. The process is completely
non-destructive and all samples can be retained for
further testing or analysis if required.”
Wess Edgar, Chief Geologist for Kirkland Lake Gold
in Australia, said: “We believe the PhotonAssay
method has potential benefits for our business that
include simple sample preparation, fast turnaround
times for high-quality results, and improved outcomes
related to health, environment, and the community.
“The sample charge used in the PhotonAssay
method is approximately 10-20 times larger than
existing fire assay, and thus has potential for a more
representative assay result of the entire crushed
sample, which is considered important for samples
containing high gold grades and/or visible gold, as are
often found at Fosterville.”
Fosterville is one of the highest grade gold mines
operating across the industry, having produced
619,000 oz in 2019 at an average grade of 39.6 g/t.
PhotonAssay’s latest market success has drawn a
positive response from CSIRO’s Chief Executive, Dr
Orica’s WebGen cuts dilution at Nexa lead-zinc mine
Orica’s fully wireless initiation system,
WebGen™, has another achievement under
its belt, having helped Nexa Resources’
Vazante underground mine reduce ore dilution from
27% to 20%, resulting in a net benefit of $1.59 million.
The single blast event at the mine achieved a
smaller hydraulic radius by keeping the pillar during
the stope extraction which, in turn, resulted in a
reduced cycle time to 20 days, down 70% from an
expected 90 days, by maintaining two mucking access
points to the main stope. This was only possible due to
the wireless capability of WebGen, Orica said.
“The unique blasting approach dramatically
improved safety by pre-loading the pillar with
WebGen, minimising the exposure of personnel and
removing the need to re-enter the area,” the company
said.
WebGen allows for groups of in-hole primers to be
wirelessly initiated by a firing command that
communicates through hundreds of metres of rock, air
and water. This eliminates the need for down-wires
and surface connecting wires, enabling new mining
methods and blasting techniques that are safe and
reliable, according to Orica.
In addition to Vazante, WebGen has improved
performance and safety at several other mining
operations, including Newmont’s Musselwhite mine
(Canada) and First Quantum Minerals’ Kevitsa mine
(Finland).
Nexa Vazante Chief Mining Engineer, Mateus
Ribeiro, said: “Thanks to this technology and
partnership, we recovered an island rib pillar, which is
a pillar kept in the open stope for dilution control. After
all the ore from the block was extracted and the pillar
had completed its requirement, the pre-loaded holes
were successfully initiated remotely.
“We went through a series of improvements in the
evolution of blasting technology with Orica, from the
first detonators until nowadays using 100% wireless
detonators. The blast happened two levels below us,
so we are 400 m away, above the shot. All encoded
signals were sent through the rock with the safety
protocols to fire the blast being followed.”
Vazante is a zinc-lead mine owned by Nexa
Resources, located in northwest Minas Gerais, Brazil.
Using vertical retreat mining and long hole open stope
as the main methods for ore extraction, the mine has
traditionally deployed wired initiators in the recovery
of ore, typically yielding around 60% ore recovery in
the pillars. The application of wired initiators also
required increased resources and time in the mine,
according to Orica.
In 2019, Orica proposed the implementation of
WebGen wireless initiating technology at Vazante to
support the team in mitigating
the operational and safety
challenges of the mine.
Enabled by the wireless
technology, ore within the
pillars can be recovered
through pre-loading without
the need to return to the open
stope. With the introduction of
WebGen, the mine was able to
gain time in the sequencing of
the blast and extract ore
previously inaccessible while
improving its operating
productivity, according to Orica.
Orica’s Latin America
Larry Marshall, according to Chrysos.
“It’s very rewarding to have a global leader like
Kirkland Lake embrace this new Aussie technology,
which sees our research continuing to improve the
efficiency and environmental sustainability of the
industry around the world,” Dr Marshall said.
Highlighting the benefits of PhotonAssay for
miners, Chrysos CEO, Dirk Treasure, stated: “Our
PhotonAssay installations provide single-touch
operation and improved safety outcomes, whilst also
reducing labour requirements and the potential for
human error. The technology’s fast turnaround on high
sample volumes provides customers with time-critical
operational data and drives optimisation through their
entire value chain.
“We are seeing increasing interest in Chrysos
PhotonAssay from both laboratories and miners.
Recent developments across the sector are driving a
desire for technological solutions that deliver
measurable productivity gains and true competitive
advantage. This is an exciting time, not just for us, but
for the entire industry.”
On Site Laboratory Services, a company based in
Bendigo, will staff and operate the unit at Fosterville on
behalf of Kirkland Lake Gold, Chrysos said.
www.chrysos.com.au; www.klgold.com
Wireless and Electronic Blasting Systems Specialist,
Wesley Andrade, said: “The Nexa Vazante crew and
our team conducted extensive site signal surveying
and applied best practices to ensure the drill pattern in
the pillar was accurately loaded with WebGen 100
units, encoded and positioned as planned.
“This achievement in recovering a pillar through
wireless initiation while protecting people from
hazards is made possible only by the strong
partnership between Nexa Vazante and Orica. We are
thrilled to have Nexa Vazante successfully implement
wireless blasting with our WebGen initiating system.”
The pillar pre-loaded with the wireless initiators was
safely fired after 33 days of sleep time, with several ore
blasts taking place alongside the pre-loaded pillar. A
second application is currently being studied to allow
pre-loading of an entire stope, which will reduce
operational risk, the number of cycles and increase ore
production and therefore profitability for Nexa
Vazante, Orica says.
www.orica.com; www.nexaresources.com
12 International Mining | SEPTEMBER 2020