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Prieska Zinc-Copper Project Metallurgical Flowsheet Test Work Achieves High Metal Yields
Orion Minerals Limited
Incorporated in the Commonwealth of Australia
Australian Company Number 098 939 274
ASX share code: ORN
JSE share code: ORN
ISIN: AU000000ORN1
PRIESKA ZINC-COPPER PROJECT METALLURGICAL FLOWSHEET TEST WORK ACHIEVES HIGH METAL
YIELDS AND EFFECTIVE METAL SEPARATION FROM ALL TARGET ZONES
- Flowsheet development phase of metallurgical studies successfully completed.
- Zinc and copper successfully separated for all sulphide metallurgical zones.
- Metallurgical studies on track with final validation and optimisation work now underway.
Orion Minerals Ltd (ASX/JSE: ORN) (Orion or the Company) is pleased to announce that the development of a mineral
processing flowsheet, for treatment of sulphide zinc-copper mineralisation at the Prieska Zinc-Copper Project (Prieska
Project) has been successfully completed.
“Figures" referred to throughout this announcement can be viewed on the pdf version of the announcement, available on
the Company's website, www.orionminerals.com.au.
The derived mineral processing flowsheet achieves high zinc and copper recoveries into separated product streams from
which the production of high-quality, differentiated zinc and copper concentrates can be yielded.
The processing flowsheet has been tested with notable success on all the mineralised zones of the Prieska deposit that
are targeted in the Bankable Feasibility Study (BFS) currently underway. The deposit is zoned, for metallurgical testing, by
the degree of oxidation, (shallow supergene and deep hypogene zones). The internal variation in zinc and copper
grades relative to each other across the deposit was also considered (zinc-dominant and copper-dominant zones).
Representative core samples for the test work were collected from holes drilled by Orion across these different grade and
oxidation zones (refer ASX release 15 November 2017).
Most significantly, effective zinc and copper separation has now been achieved from samples collected within the
supergene horizon of the deposit, whilst maintaining acceptable metal yields from both the copper and zinc circuits for
differentiated concentrates. This is a notable improvement on the metallurgical performance achieved by historical mining
operations and from earlier test work (refer ASX release 15 November 2017).
The derived flowsheet, when applied to samples collected from the supergene horizon, achieved maximum metal recoveries
of 88% zinc within the zinc circuit and 74% copper within the copper circuit. Samples collected from the hypogene horizon
attained maximum metal recoveries of 85% for zinc within the zinc circuit and 88% for copper within copper circuit.
These metal recoveries, were achieved using only open-circuit testing, (a preliminary step applied to only demonstrate
processing flowsheet efficacy) and compare very well to metal recoveries reported to have been achieved during historical
mining operations1. Further improvements in metal recovery and the production of optimised, premium quality concentrates
can be expected during the follow-up locked-cycle testing that is currently underway.
Locked-cycle testing better simulates the continuous operating conditions of a mineral processing plant and so more
accurately defines design metal recoveries and metal concentrate qualities. Locked-cycle test results will form the basis of
assumptions to be incorporated into the BFS which is targeted for completion in Q4 2018. A more detailed description of
the open-circuit test work methodology used to date is provided in Appendix 1.
Results achieved are summarised in Table 1.
Test Head Grade Cu Circuit Zn Circuit Combined Tails
Recovery(2) Recovery(1)
Test Description Cu (%) Zn (%) Cu Zn Zn Rec. Cu Rec. Cu Zn
Rec. Rec. Grade Grade
(%) (%) (%) (%) (%) (%)
Cu-rich Deeps Open Circuit Cleaner 2.3 2.5 87 16 69 3 0.3 0.9
Zn-rich Deeps Open Circuit Cleaner 1.5 5.7 88 7 85 5 0.1 0.5
Supergene Open Circuit Cleaner 2.1 3.7 74 7 88 20 0.2 0.2
Table 1: Summary of flowsheet development metallurgical test work results from open circuit tests.
Metallurgical Test Work Approach
Metallurgical studies on the Prieska deposit are being conducted in three defined phases as part of the BFS, these being:
- Phase 1- flotation amenability scouting: to determine whether froth flotation (used in historical mining
operations) is a mineral processing technique that can continue to be used to recover and concentrate zinc and
copper sulphides from the dip and strike extensions of the Prieska deposit that is targeted for future mining;
- Phase 2 - flowsheet development: to derive a froth flotation-based processing route, able to produce separated
zinc and copper concentrates, within targeted quality ranges and achieve high metal recoveries from all
metallurgical zones of the deposit, including open pitable supergene sulphides; and
- Phase 3 – optimisation and detailed design: being the final stage of metallurgical design, which aims to optimise,
validate and then conclude a detailed design of the ore processing plant, to enable production scheduling and
accurate costing.
Results of the successful completion of Phase 1 were reported in November 2017, confirming that the targeted
mineralisation at the Prieska deposit was amenable to processing by froth flotation.
The results achieved from Phase 2 test work, reported here, are indicative of how the derived flowsheet performs with
respect to recovering and separating targeted metals. Ongoing optimisation aims to improve the resultant concentrate
qualities to equal or better the metallurgical performance that was reported to have been achieved during historical mining
operations. Over the 20-year mine life, metal recoveries averaged 85% for both zinc and copper into concentrates that had
concentrate grades ranging between 28% to 30% for copper (in the copper concentrates) and 51% to 53% for zinc (in the
zinc concentrates)(3).
Achieving effective zinc and copper separation into separate concentrate streams for the supergene zone of the deposit is
significant in regard to the BFS studies which are considering early mining and cashflow generation from a low capital
intensity open pit. The supergene horizon, extending from near-surface to approximately 100 metres below surface, holds
an Indicated Mineral Resource of 1.2 million tonnes grading 2.6% zinc and 2.4% copper (refer Table 2).
The deep hypogene sulphide zone, targeted for exploitation by underground mining, is currently estimated as an Inferred
Mineral Resource amounting to 22.6 million tonnes grading 3.7% zinc and 1.2% copper, (refer Table 2)4.
The metallurgical test work results achieved to date confirm that the Prieska deposit is amenable to efficient treatment
applying widely-used, well-understood mineral processing techniques and using standard, widely available reagents.
Process Flowsheet
The derived process flowsheet (Figure 1) is an improvement on the historical ore processing route. This process flowsheet
will form the basis of process design, equipment selection and equipment sizing, and will be refined and optimised as the
results of scheduled metallurgical test work become available.
(1) Refer ASX release of 15 November 2017.
(2) Represents the total metal recovered to the high grade cleaner concentrate, high grade cleaner tailings, low grade re-cleaner
concentrate, low grade re-cleaner tailings and scavenger rougher concentrate in open circuit testing. Lock-cycle testing aims to recover
most of this metal into the final concentrate.
(3) Refer ASX release 15 November 2017.
(4) Refer ASX release 8 February 2018.
Figure 1: Schematic of the froth flotation flowsheet derived to process the Prieska Zinc-Copper deposit.
Prieska Project Background
The Prieska Project is in the Northern Cape province of South Africa approximately 290km south-west of the city of
Kimberley, (Figure 2). Prieska Copper Mine operated as an underground zinc and copper mine, exploiting the Copperton
deposit, between 1971 and 1991 to produce 1.01 million tonnes of zinc and 430,000 tonnes of copper in concentrates 5.
Orion is investigating establishing new mining operations to continue the extraction of the remaining zinc-copper
mineralisation at Prieska, a volcanogenic massive sulphide – style (VMS) deposit, with significant remaining potential. Orion
has now delineated, as part of an on-going mine development program a JORC-compliant, global Mineral Resource
amounting to 24 million tonnes grading 1.2% copper and 3.5% zinc, comprising, amongst others, a hypogene Inferred
Mineral Resources of 22.6 million tonnes grading 3.7% zinc and 1.2% copper (Deep Sulphide zone) and a supergene
Indicated Mineral Resources amounting to 1.2 million tonnes grading 2.6% zinc and 2.4% copper (+105 Supergene zone)6.
Mineral Resources definition work is ongoing, with objective of upgrading Mineral Resource confidence and to further
expand the global Mineral Resource.
Mine development studies are in progress and are scheduled to deliver a BFS in Q4 2018. DRA Projects South Africa Pty
Ltd are the lead consultant appointed to compile the BFS, part of which includes design of the ore processing plant.
Metallurgical test work is being conducted at the Mintek laboratories in Johannesburg, South Africa.
(5) Obtained from mine production records.
(6) Refer ASX release 8 February 2018.
Figure 2: Location of Prieska Zinc-Copper Project.
Global Mineral Resource For Prieska Project - Repli Trading No 27 (PTY) Ltd
Classification Zn Cu Au Ag
Tonnes Metal Tonnes Grade (%) Metal Tonnes Grade (%) Metal Ounces Grade (g/t) Metal Ounces Grade (g/t)
Deep Sulphide Inferred 22,649,000 839,000 3.71 266,000 1.17 153,000 0.21 6,904,000 9.48
+105 Supergene Indicated 1,241,000 32,000 2.57 30,000 2.37 9,000 0.23 348,000 8.73
+ 105 Oxide Inferred 272,000 2,000 0.86 2,000 0.63 1,000 0.12 17,000 1.82
Total Global 24,162,000 874,000 3.47 297,000 1.23 163,000 0.21 7,269,000 9.36
Note All Resources Stated at Zero Cut-off. All masses rounded to thousands which may result in rounding errors in totals
Table 2: Global Indicated and Inferred Mineral Resource estimate for the Prieska Project (refer ASX release 8 February 2018
for further details).
Orion’s Managing Director and CEO, Errol Smart, commented:
"The Phase 2 metallurgical test work results have yet again met all our expectations and are an important advance within
the BFS studies underway. The importance of achieving effective metal separation as a precursor to locked cycle test work
to optimise concentrate qualities is significant. The suitability of the open pit supergene target to the same process routes
and concentrate sales strategies is particularly important.
Errol Smart
Managing Director and CEO
1 March 2018
ENQUIRIES
Investors JSE Sponsor
Errol Smart – Managing Director & CEO Rick Irving
Denis Waddell – Chairman Merchantec Capital
T: +61 (0) 3 8080 7170 T: +27 (0) 11 325 6363
E: info@orionminerals.com.au E: rick@merchantec.co.za
Media
Michael Vaughan Barnaby Hayward
Fivemark Partners, Australia Tavistock, UK
T: +61 (0) 422 602 720 T: +44 (0) 787 955 1355
E: michael.vaughan@fivemark.com.au E: orion@tavistock.co.uk
Suite 617, 530 Little Collins Street
Melbourne, VIC, 3000
Competent Persons Statement
The information as presented in this report that relates to the results of metallurgical test work at the Prieska Project is not
in contravention of the 2012 Edition of the Australasian Code for Reporting of Exploration Results, Mineral Resources and
Ore Reserves (JORC Code) and has been compiled and assessed under the supervision of Mr Errol Smart, Orion’s
Managing Director. Mr Smart (PrSciNat) is registered with the South African Council for Natural Scientific Professionals, a
Recognised Overseas Professional Organisation (ROPO) for JORC purposes and has sufficient experience that is relevant
to the style of mineralisation and type of deposit under consideration and to the activity being undertaken to qualify as a
Competent Person as defined in the 2012 Edition of the JORC Code. Mr Smart consents to the inclusion in this
announcement of the matters based on his information in the form and context in which it appears.
Disclaimer
This release may include forward-looking statements. Such forward-looking statements may include, among other things,
statements regarding targets, estimates and assumptions in respect of metal production and prices, operating costs and
results, capital expenditures, mineral reserves and mineral resources and anticipated grades and recovery rates, and are
or may be based on assumptions and estimates related to future technical, economic, market, political, social and other
conditions. These forward-looking statements are based on management’s expectations and beliefs concerning future
events. Forward-looking statements inherently involve subjective judgement and analysis and are necessarily subject to
risks, uncertainties and other factors, many of which are outside the control of Orion. Actual results and developments may
vary materially from those expressed in this release. Given these uncertainties, readers are cautioned not to place undue
reliance on such forward-looking statements. Orion makes no undertaking to subsequently update or revise the forward-
looking statements made in this release to reflect events or circumstances after the date of this release. All information in
respect of Exploration Results and other technical information should be read in conjunction with Competent Person
Statements in this release. To the maximum extent permitted by law, Orion and any of its related bodies corporate and
affiliates and their officers, employees, agents, associates and advisers:
- disclaim any obligations or undertaking to release any updates or revisions to the information to reflect any change in
expectations or assumptions;
- do not make any representation or warranty, express or implied, as to the accuracy, reliability or completeness of the
information in this release, or likelihood of fulfilment of any forward-looking statement or any event or results expressed
or implied in any forward-looking statement; and
- disclaim all responsibility and liability for these forward-looking statements (including, without limitation, liability for
negligence).
Appendix 1: Test Work Methodology
Open circuit bench scale flotation tests were conducted in 1kg batches. Each sample was milled using a laboratory rod
mill at 50% solids by mass to achieve a target grind of 80% passing 75 microns for the zinc-rich hypogene sample and
70% passing 75 microns for the supergene and copper-rich hypogene samples.
The milled slurry was then transferred into a 2.5 litre flotation cell, which was agitated using a Denver D12 flotation
machine at an impellor speed of 1200 rpm. Depending on the feed mass, cleaner flotation testing was conducted in
either a 1 litre or 2 litre flotation cell which was agitated using a Denver D12 flotation machine at an impellor speed of
1000 -1200 rpm. The supergene test procedure included a rougher concentrate regrind step which was conducted in a
stirred mill using ceramic media to achieve a target grind of 80% passing 25 microns. Concentrates were collected by
scraping off the froth at 15 second intervals. All test products were pulverised and assayed for copper, lead, zinc, iron
and sulphur using the ICP analysis method.
The total copper circuit recoveries as presented in Table 1, reflect the total recovery to the copper re-cleaner concentrate,
re-cleaner concentrate tailings and scavenger cleaner concentrate streams in open circuit testing. The total zinc circuit
recoveries as presented in Table 1, reflect the total recovery to the high grade cleaner concentrate, high grade cleaner
tailings, low grade re-cleaner concentrate, low grade re-cleaner tailings and scavenger rougher concentrate in open
circuit testing.
Date: 01/03/2018 09:05:00 Produced by the JSE SENS Department. The SENS service is an information dissemination service administered by the JSE Limited ('JSE').
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