Discovery Reports Optimized Results from its Feasibility Study Metallurgical Test Program
Discovery Reports Optimized Results from its Feasibility Study
Metallurgical Test Program
October 26, 2023, Toronto, Ontario - Discovery Silver Corp. (TSX: DSV, OTCQX: DSVSF)
(“Discovery” or the “Company”) is pleased to announce results from its Feasibility Study (“FS”)
metallurgical test program from its Cordero project (“Cordero” or “the Project”) located in
Chihuahua State, Mexico. Highlights from the test work include:
• Increased silver recoveries of up to 7% to the precious metals concentrate where higher
payabilities are received.
• Significant reductions in reagent consumption while achieving improved metallurgical
performance than outlined in the Preliminary Feasibility Study (“PFS”)
• Excellent metallurgical performance achievable for oxide-sulphide blending of up to 15%
oxides (the PFS assumed a cap of up to 10% oxides).
• Primary grind sensitivity confirmed a coarse grind size of 2 00 micron passing p80 is the
optimal grind size (unchanged from the PFS).
• Blasting study showed run- of-mine material to be smaller than previously estimated
allowing for a smaller primary crusher.
Tony Makuch, CEO, states: “Our Feasibility Study test work demonstrates the exceptional
metallurgical characteristics of our Cordero deposit. Previous test work established excellent
recoveries for different mining phases and variable grade profiles to generate clean, saleable
concentrates. This current program was focused on optimization and was successful in
significantly increasing silver recoveries to the precious metals concentrate, where higher
payabilities are received, and significantly reducing reagent consumption. The progr am also
established that co -processing of oxides can be increased to up to 15% oxides allowing for
flexibility for mine planning and potentially extending the 18-year mine life that was outlined in
the PFS. Meanwhile, our other feasibility study work programs continue to advance well and
we remain on track for delivering our study in the first quarter of next year.”
PFS METALLURGICAL TEST PROGRAM
Summary: the Company’s two previous metallurgical test programs were primarily focused
on variability testwork. Results from these programs established excellent recoveries for all
major rock types, rock type blends, different mining phases, variable grade profiles and for
oxide-sulphide blending of up to 10% oxides. The FS metallurgical test program was focused
NEWS RELEASE
on optimizing metallurgical performance for a run -of-mine composite with process variables
such as reagent dosage and type, grind size and the testing of oxide-sulphide blends with
oxides above 10%.
In total 12 locked cycles test were completed. Optimization testwork was completed on a
master composite representing a blend of rock types consistent with the life- of-mine average
and an oxide-sulphide blend of 10% oxides and 90% sulphides . The grade of this composite
was approximately 35 g/t Ag, 0.5% Pb and 0.7% Zn. Local treated water and well water were
also used in select locked cycle tests to confirm that local water quality would not impact metal
recoveries. The testwork wa s conducted by Blue Coast Research Ltd. (“Blue Coast”) , an
independent third party, with oversight from Libertas Metallurgy Ltd. (“Libertas”), Chris Martin
(Independent Consulting Metallurgist) and Ausenco Engineering Canada Inc. (“Ausenco”).
Recoveries: silver recoveries to the precious metals (“PM”) concentrate increased by up to
7% in comparison to the PFS testwork through reagent optimization. Payabilities for silver in
the PM concentrate of 95% are significantly higher than payabilities for silver in the zinc
concentrate of 70% after a deduction of three silver ounces per tonne. Silver recoveries into
the zinc concentrate were approximately 4% lower resulting in an increase in overall silver
recoveries of up to 3%. Recoveries for lead were slightly higher than the PFS testwork while
zinc recoveries were slightly lower. A comparison of the FS and PFS test results, which were
based on the same composite sample, are summarized in the table below.
Sample
Recoveries Concentrate Grades
Ag Pb Zn
PM con Zn con
PM con Zn con Total Ag Pb Ag Zn
(%) (%) (%) (%) (%) (g/t) (%) (g/t) (%)
FS composite –
ground water 79 6 85 86 84 2,717 47 183 52
FS composite –
treated water 81 6 87 86 83 3,033 47 170 53
PFS master
composite 74 10 84 84 86 3,522 56 328 52
Reagents: the FS testwork was successful in achieving improved recoveries as outlined
above at significantly reduced consumption of key reagents. Consumption of MIBC and
CuSO4, the two most expensive reagents as per the PFS, was lowered by 88% and 16%
respectively. Material reductions were also achieved for NaCN and Aero 5100. Test results
including the costs that each reagent represented in the PFS are summarized in the table
below.
Reagent
Consumption (g/t)
% change
PFS Cost
FS
testwork
PFS
testwork
$/t
processed
US$M
(LOM)
CuSO4 130 155 -16% $0.33 $103
MIBC 16 133 -88% $0.23 $71
Lime 1,907 1,597 19% $0.22 $68
ZnSO4 150 150 0% $0.20 $61
X5000 17 17 0% $0.14 $42
NaCN 30 50 -40% $0.13 $38
Aero 5100 16 14 -13% $0.09 $27
Comminution: an additional 10 bond work index (“BWI”) tests and 15 SAG mill comminution
(“SMC”) tests were completed to increase the previous data set and increase confidence in
the process design assumptions for the comminution circuit. Locked cycle flotation tests were
completed on the run-of-mine composite with primary grind sizes of 150 µm, 200 µm and 230
µm. Regrind sensitivity testing and energy input per tonne assessment work was also
completed. Results from this testwork were consistent with the process design assumptions
for the PFS, including confirmation that a coarse grind size of 200 µm is the optimal primary
grind size for the Project.
Oxide-sulphide blends: locked cycle tests were completed on blends of 15% oxides / 85%
sulphides and 20% oxides / 80% sulphides. Results demonstrate that excellent metallurgical
performance can be achieved with blending of up to 15% oxides (the PFS assumed a cap of
10% oxides). At a blend of up to 20% oxides, recoveries for lead and zinc start to become less
economic.
Increasing the blend to up to 15% oxides offers more flexibility for mine planning purposes and
has the potential to increase the mine life given there was approximately 30 million tonnes of
unprocessed stockpiled oxide material above cut-off in the PFS mine plan.
Sample
Recoveries Concentrate Grades
Ag Pb Zn
PM con Zn con
PM con Zn con Total Ag Pb Ag Zn
(%) (%) (%) (%) (%) (g/t) (%) (g/t) (%)
FS – 15% Ox / 85% Sx 77 6 83 82 85 3,231 50 198 53
FS – 20% Ox / 80% Sx 75 6 81 78 81 2,948 43 209 50
PFS – 10% Ox / 90% Sx 74 10 84 84 86 3,522 56 328 52
PROCESS DESIGN
The process design for the FS will consist of conventional flotation with staged expansions,
consistent with the PFS approach. The first phase consists of a conventional grinding circuit
made up of a primary crusher, SAG mill and ball mill, followed by a flotation circuit. The planned
throughput rate of this initial phase is expected to be approximately 25,500 tonnes per day
(“tpd”).
The second phase of the plant expansion will include the addition of a parallel circuit consisting
of a SAG mill and a ball mill and a duplicate flotation circuit. The planned throughput rate of
this expanded phase is expected to be approximately 51,000 tpd.
The proposed process design for the FS is a conventional, well-proven flowsheet that is capital-
efficient, robust and delivers comparatively reasonable operating costs with reliability of
operations. The design is effectively the same as what was assumed for the PFS with the main
change being the incorporation of a smaller primary crusher. This change was based on results
from an ore blasting study that demonstrated run-of-mine material to be delivered to the plant
is smaller than what was assumed in the PFS.
About Discovery
Discovery’s flagship project is its 100%-owned Cordero project, one of the world’s largest silver
deposits. The PFS completed in January 2023 demonstrates that Cordero has the potential to
be developed into a highly capital efficient mine that offers the combination of margin, size and
scalability. Cordero is located close to infrastructure in a prolific mining belt in Chihuahua State,
Mexico.
On Behalf of the Board of Directors,
Tony Makuch, P.Eng
President, CEO & Director
For further information contact:
Forbes Gemmell, CFA
VP Corporate Development
Phone: 416-613-9410
Email: [email protected]
Website: www.discoverysilver.com
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