Eloro Resources Provides Update on the Ongoing Preliminary Metallurgical Testwork Program for the Iska Iska Silver-Tin Polymetallic Project, Potosi Department, Bolivia
Eloro Resources Provides Update on the Ongoing Preliminary Metallurgical Testwork
Program for the Iska Iska Silver-Tin Polymetallic Project, Potosi Department, Bolivia
Toronto, Canada, April 4, 2023– Eloro Resources Ltd. (TSX: ELO; OTCQX: ELRRF; FSE:
P2QM) (“Eloro”, or the “Company”) is pleased to provide an update on its ongoing preliminary
metallurgical testwork program for the Iska Iska silver-tin polymetallic project (the “Project”) in the
Potosi Department, southern Bolivia. The ongoing work, including flowsheet development
testwork and mineralogical characterization, is being carried out by Blue Coast Research Ltd.
(“Blue Coast” or “BCR”) based in Parksville, British Columbia, and Mineral Concentration
Laboratory of the National Faculty of Engineering from the Technical University of Oruro (“UTO”),
Bolivia. The objective of the coordinated work programs is to develop a geo-metallurgical
understanding of the mineralized domains and to obtain preliminary metallurgical recovery
estimates for the main valuable constituents of the mineralized material currently identified at the
Project.
Tom Larsen, CEO of Eloro, commented: “The Iska Iska silver-tin polymetallic deposit is a
remarkably extensive system with multiple potential ore types which require more metallurgical
work than originally anticipated, especially for tin, as outlined in this press release. The
preliminary metallurgical recovery estimates are a prerequisite for the release of the Project’s
maiden mineral resource (“MRE”). Consequently, the release of the MRE has been delayed until
this metallurgical work, which is in progress, has been completed. All other work required for the
MRE has been largely completed by Micon International Limited, including much of the reporting.”
Mr. Larsen continued, “I am very pleased to announce the appointment of Mr. Mike Hallewell,
B.Sc., F.I.M.M.M., F.S.A.I.M.M., F.M.E.S., C.Eng ,, an internationally recognized expert on tin
metallurgy, as Senior Strategic Metallurgist for Eloro. Going forward Mike will be working closely
with our metallurgical consultants to optimize our tin recovery and with our geological team to
define geo-metallurgical domains for mineral resource definition and future potential production.”
Geometallurgical Domains Iska Iska
The Iska Iska silver-tin polymetallic deposit has many characteristics of the typical Bolivian tin
deposits. Extensive tin mineralization likely developed deep in the earth’s crust with cassiterite
forming at high temperatures from 350C to 500C. This major initial stage of magmatism drove
the formation of the major stratovolcano at Iska Iska some 18 to 15 million years ago.
Subsequently, when the magma chamber was depleted, the volcano collapsed, forming a classic
collapsed caldera. Resurgence of the collapsed volcano included the intrusion of the Iska Iska
porphyry, followed by dacitic domes and brecciation such as the Santa Barbara breccia pipe.
These events were closely associated with widespread porphyry-epithermal Ag-Zn-Pb
mineralization, which partially overprinted the pre-existing tin mineralization.
Figure 1 shows the distribution of Sn:Cu at Iska Iska. The Sn:Cu ratio is an indicator of the
presence of oxide tin (cassiterite – shown in green, within the core) vs sulphide tin (stannite –
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shown in red, making up the periphery). Tin is found predominantly on the west side of the Santa
Barbara deposit. Deep drilling and magnetic modelling indicate that the tin porphyry is present
beneath the Iska Iska Porphyry. As previously reported, the signature of the overall tin porphyry
system based on magnetic data likely extends for some 5 km by 3 km which includes the
Casiterita area to the southwest, which is currently being drill-tested (see Eloro’s press release
dated February 14, 2023). The longitudinal section in Figure 1 covers a strike length of 2.5km.
Figure 1: Longitudinal Section Showing Distribution of Sn/Cu ratio (Looking West-
southwest). The core of the Iska Iska deposit contains higher Sn and low Cu whereas
the low Sn/Cu ratio is predominantly at the top and on the margins of the tin
mineralization.
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Metallurgical Testwork
The overall metallurgical testwork / mineralogical characterization program has evolved into the
development of several potential flowsheets to best fit the extensive mineralization identified
within the Project area. The main metallurgical studies in the ongoing development program are:
1) Recovery of lead, zinc and silver from polymetallic sulphide mineralization; and
2) Recovery of tin from cassiterite-rich Iska -Iska mineralization and the adjoining Casiterita
property to the south-southwest of Iska Iska.
Future work will include recovery of gold and copper, where they are found enriched within the
system.
The geo-metallurgical program is being directed by Mr. Mike Hallewell, C.Eng., a senior mineral
processing consultant based in Cornwall, England, who has extensive specialist knowledge in
the recovery of tin at mining operations and exploration projects worldwide, and Richard Gowans,
P.Eng., Principal Metallurgist for Micon International Limited, an independent Qualified Person
as defined under NI 43-101. The mineralogical characterization testwork is being managed by
Nichola McKay P. Geo., MBA, an experienced Professional Geoscientist who specializes in the
development of geo-metallurgical programs.
Mineralogical and Geometallurgical Characterization
Mineralogical testing of the Iska Iska resource consists of three main campaigns:
1) On-site downhole hyperspectral analysis with high resolution core imaging,
2) QemSCAN mapping of polished thin sections selected from drill core across the resource
representing key lithologies and mineralization types, with supporting X-ray diffraction and
microprobe analysis, and
3) QemSCAN analysis of ground metallurgical test feeds and selected test products.
A group of geometallurgical variability samples are being tested using a standardized testing
protocol that will link metallurgical behaviour with mineralogy for samples from different zones in
the resource.
In parallel to the laboratory-based geomet work, all QemSCAN data is being used as a training
set for calibration / correlation with the hyperspectral program, with the objective of identifying
key markers of tin mineral zonation that can be populated through the resource.
Lead-Zinc-Silver Flotation
The initial metallurgical testwork, using composite samples of sulphide mineralization from the
Santa Barbara polymetallic zone, comprised the development of a preliminary flotation flowsheet
to maximize lead, zinc and precious metals into saleable concentrates. The results of this initial
work were presented in the Company’s press release dated June 13, 2022. These preliminary
results indicated good lead, zinc and silver recoveries using conventional flotation technology.
The estimated recoveries based on preliminary locked cycle flotation tests are 79.6% lead and
55.8% silver into a lead concentrate, and 87.0% zinc and 32.0% silver into a zinc concentrate
(total silver recovery of 87.8%). These recoveries are based on preliminary scoping level bench
scale tests completed by BCR in 2022 using two composite samples of polymetallic
mineralization. These tests were not optimized and improved performance in terms of higher
recoveries would be expected with further mineralogical and metallurgical studies.
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The next phase of Pb-Zn-Ag flowsheet development testwork, following completion of the
inaugural mineral resource estimate, is to optimize the preliminary flowsheet, with integrated
mineralogy/metallurgy studies using a variety of samples representing a range of lithologies and
ore-types, and to undertake silver deportment studies. The deportment and recovery of potential
by-products will also be investigated.
Tin Metallurgy
The recovery of cassiterite is usually conducted us ing a mixture of gravity and tin flotation with
removal of sulphide minerals either prior to these processes and/or as part of concentrate clean-
up. Coarser cassiterite grain sizes tend to be more amenable to gravity concentration, whereas
finer cassiterite particles are recovered by tin flotation down to ~6 microns, which is normally
discarded since it is too fine for current beneficiation technologies. The different Iska Iska ore
types are currently being characterised to better understand the cassiterite grain size and
cassiterite associations with other minerals as a function of ore type so as to better understand
and estimate the level of tin recovery in terms of geological space. Stannite is present, but at this
time will be assumed to deport as a tin loss to sulphides.
Initial tin deportment studies undertaken on various samples of mineralization obtained from the
Project exploitation drilling campaign have sugges ted the occurrence of various forms of tin
mineralization within the extensive mineralized domains currently identified at the Project. The
tin mineralogy and physical competence is linked to geological attributes. The styles of tin
mineralization identified at the Project can be characterized as follows:
Type A - High grade coarse-grained cassiterite (tin oxide).This style of tin mineralization is the
easiest to process due to the coarser liberated tin mineralization that is amenable to conventional
mineral processing technologies, such as gravity separation and flotation. This type of tin
mineralization is expected to predominate deeper in the deposit and also at Casiterita where
artisanal miners have previously produced high grade (~50%) tin concentrates from cassiterite-
quartz veins (see Eloro’s press release November 22, 2022).
Type B – High/medium grade fine-grained cassiterite. Tin-rich sulphide mineralization is typically
found below and west of the eastern Santa Barbara area Pb-Zn-Ag rich polymetallic sulphide
zones. This style of tin mineralization requires fine to very fine grinding, sulphide removal via
flotation, tin flotation and fine particle gravity separation.
Type C – Medium grade fine-grained cassiterite with significant wood tin (low temperature form
of cassiterite). Tin of this type occurs predominantly in areas with moderate to strong oxidation
which has leached sulphides and redeposited the tin as wood tin. High grade Type A tin also
may exist in this zone. This form of tin has similar metallurgy to Type B, but good recoveries can
be obtained if Type A mineralization is present.
Type D - Medium grade stannite (copper-tin-iron sulphide mineral). Stannite is not recoverable
using conventional tin mineral processing technology. Predominant stannite tin mineralization
tends to occur at the top and peripheral to the core of the tin mineralization. Where stannite
mineralization has been oxidized and leached, the mineralization type becomes more Type B or
C depending on intensity of oxidation.
Tin metallurgical studies completed to date include preliminary tests on two composite samples
and the development of a standard test protocol to assess the amenability of tin mineralized
samples to obtain a tin concentrate of acceptable grade.
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A high-grade tin composite made up of crushed assay reject samples from exploration drilling
was prepared and used for preliminary metallurgical tests at UTO in Bolivia. The 67 kg composite
sample, considered Type A tin (see description above), comprised mineralized samples from drill
holes DSB-32 (from 62.3 m to 76.7 m) and DSB-33 (from 356.7 to 365.6 m). The sample was
from an oxidized zone and had an average tin grade of 1.68% Sn.
Scoping tests completed on this sample included gravity separation tests using a shaking table
and centrifugal concentrator, and cassiterite flotation tests. Although not optimized, the gravity
only tests using both tables and centrifugal concentrator resulted in a 39% tin grade concentrate
with about 60% recovery. Tests using a table only produced a concentrate containing about 50%
Sn although recovery was only around 30%. Flotation tests at a non-optimum grind size resulted
in about 50% tin recovery into a 6% Sn concentrate. These preliminary test results suggest a
direct tin smelter feed concentrate can be produced from this type of tin mineralization with about
a 60% recovery. The estimated tin recovery into a lower grade concentrate suitable for feeding
a tin-fuming process is about 75%.
Recent development tests by BCR using a composite sample of crushed assay rejects from drill
hole DSBU-03 containing 0.52% Sn, produced a tin-fuming feed concentrate with a tin recovery
of about 28%. Mineral characterization of this sample via optical microscopy suggests that the
tin mineralization comprises mainly fine-grained cassiterite with minor fine wood tin (Types B and
C).
The preliminary flowsheet used by BCR comprised sulphide flotation, which rejected
approximately 92% of the sulphide sulphur with less than 15% tin losses, gravity roughing using
a centrifugal concentrator and upgrading of sized rougher product using a laboratory supper-
panner, cassiterite flotation with upgrading of sized re-ground flotation rougher product using a
laboratory supper-panner.
Following a detailed review of the test results and testing procedure, a standard tin amenability
test protocol has been defined. This flowsheet will be used over the coming weeks by BCR to
test a variety of samples. Samples have been selected to include a range of tin grades and types
of tin mineralization.
Copper-Gold and Other Valuable By-Products
Drilling has shown zones of mineralization with gold grades above 1 g/t as well as zones with
elevated levels of copper. A metallurgical-mineralogical characterization program is being
planned to assess the potential for recovering these valuable metals.
The future geo-metallurgical program also will include studies to understand the deportment of
other potential metals such as bismuth and indium.
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Qualified Person
Richard Gowans, P.Eng., Principal Metallurgist for Micon International Limited, is an independent
Qualified Person as defined under NI 43-101. Mr. Gowans. Has reviewed and approved the
technical content of this news release.
Dr. Osvaldo Arce, P. Geo., General Manager of Eloro’s Bolivian subsidiary, Minera Tupiza S.R.L.,
and a Qualified Person in the context of NI 43-101, supervised all exploration work at Iska Iska.
Dr. Bill Pearson, P.Geo., Executive Vice President Exploration Eloro, and who has more than 45
years of worldwide mining exploration experience including extensive work in South America,
manages the overall technical program working closely with Dr. Osvaldo Arce, P.Geo., Manager
of Minera Tupiza. Dr. Quinton Hennigh, P.Geo., Senior Technical Advisor to Eloro and
Independent Technical Advisor, Mr. Charley Murahwi P. Geo., FAusIMM of Micon International
Limited are regularly consulted on technical aspects of the project.
Eloro is utilizing both ALS and AHK for drill core analysis, both of whom are major international
accredited laboratories. Drill samples sent to ALS are prepared in both ALS Bolivia Ltda’s
preparation facility in Oruro, Bolivia and the preparation facility operated by AHK in Tupiza with
pulps sent to the main ALS Global laboratory in Lima for analysis. More recently Eloro has had
ALS send pulps to their laboratory at Galway in Ireland. Eloro employs an industry standard
QA/QC program with standards, blanks and duplicates inserted into each batch of samples
analyzed with selected check samples sent to a separate accredited laboratory.
Drill core samples sent to AHK Laboratories are prepared in a preparation facility installed and
managed by AHK in Tupiza with pulps sent to the AHK laboratory in Lima, Peru. Au and Sn
analysis on these samples is done by ALS Bolivia Ltda in Lima. Check samples between ALS
and AHK are regularly done as a QA/QC check. AHK is following the same analytical protocols
used as with ALS and with the same QA/QC protocols. Turnaround time continues to improve,
as laboratories return to more normal staffing levels.
About Iska Iska
Iska Iska silver-tin polymetallic project is a road accessible, royalty-free property, wholly
controlled by the Title Holder, Empresa Minera Villegas S.R.L. and is located 48 km north of
Tupiza city, in the Sud Chichas Province of the Department of Potosi in southern Bolivia. Through
its Bolivian subsidiary, Eloro has an option to earn a 100% interest in Iska Iska.
Iska Iska is a major silver-tin polymetallic porphyry-epithermal complex associated with a
Miocene possibly collapsed/resurgent caldera, emplaced on Ordovician age rocks with major
breccia pipes, dacitic domes and hydrothermal breccias. The caldera is 1.6km by 1.8km in
dimension with a vertical extent of at least 1km. Mineralization age is similar to Cerro Rico de
Potosí and other major deposits such as San Vicente, Chorolque, Tasna and Tatasi located in
the same geological trend.
Eloro began underground diamond drilling from the Huayra Kasa underground workings at Iska
Iska on September 13, 2020. On November 18, 2020, Eloro announced the discovery of a
significant breccia pipe with extensive silver polymetallic mineralization just east of the Huayra
Kasa underground workings and a high-grade gold-bismuth zone in the underground workings.
On November 24, 2020, Eloro announced the discovery of the SBBP approximately 150m
southwest of the Huayra Kasa underground workings.
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Subsequently, on January 26, 2021, Eloro announced significant results from the first drilling at
the SBBP including the discovery hole DHK-15 which returned 129.60 g Ag eq/t over 257.5m
(29.53g Ag/t, 0.078g Au/t, 1.45%Zn, 0.59%Pb, 0.080%Cu, 0.056%Sn, 0.0022%In and 0.0064%
Bi from 0.0m to 257.5m. Subsequent drilling has confirmed significant values of Ag-Sn
polymetallic mineralization in the SBBP and the adjacent CBP. A substantive mineralized
envelope which is open along strike and down-dip extends around both major breccia pipes.
Continuous channel sampling of the Santa Barbara Adit located to the east of SBBP returned
442 g Ag eq/t (164.96 g Ag/t, 0.46%Sn, 3.46% Pb and 0.14% Cu) over 166m including 1,092 g
Ag eq/t (446 g Ag/t, 9.03% Pb and 1.16% Sn) over 56.19m. The west end of the adit intersects
the end of the SBBP.
Since the initial discovery hole, Eloro has released a number of significant drill results in the
SBBP and the surrounding mineralized envelope which along with geophysical data has defined
an extensive target zone. In its September 20, 2022 press release, the Company reported that
new downhole geophysical data have significantly extended the strike length of the high-grade
zone at Santa Barbara a further 250m along strike to the south-southeast from existing drilling.
The 3D inverse magnetic model which correlates very strongly with the conductive zone
suggested that the high-grade feeder zone may extend across the entire caldera for as much as
a further 1 km along strike for a total potential strike length of at least 2 km. As reported, the
definition drill program was modified to sectionally drill this potential extension to define a major
open pittable deposit in the valley of the caldera. As a result, the estimated completion date for
the maiden National Instrument 43-101 mineral resource was pushed back to the end of Q1 2023.
The Company completed 84,495m in 122 drill holes for the definition drill program in the Santa
Barbara target area as announced on November 27, 2022.
On November 22, 2022, Eloro announced the acquisition of the Mina Casiterita and Mina Hoyada
properties covering 14.75 km2 southwest and west of Iska Iska. These properties connect with
the TUP-3 and TUP-6 claims previously staked by Eloro. Eloro has also staked additional land
in the area. Following the acquisition, the total land package in the Iska Iska area to be controlled
by Eloro will total 1,935 quadrants covering 483.75 km2.
Artisanal mining in the 1960’s identified high grade tin (Sn) veins on the Mina Casiterita property
that are hosted in an intrusive dacite. Production from 1962 to 1964 is reported by the
Departamento Nacional de Geología in Bolivia to be 69.85 tonnes grading 50.60% Sn.
Magnetic surveys recently completed by Eloro have outlined an extensive, near surface,
magnetic intrusive body on the Mina Casiterita property immediately southwest of Iska Iska. This
intrusive hosts the previously mined high-grade tin veins and is very likely the continuation of the
porphyry tin intrusion projected to be below the epithermal Ag-Sn-Zn-Pb mineralization at Iska
Iska.
The Porco adit from which previously reported channel sampling returned 103m grading 521 g
Ag eq/t (including g 117g Ag/t, 1.44 g Au/t, 0.54% Cu and 0.66% Sn) in altered basement
sediments, is located near the northeast part of the magnetic anomaly, attesting to the potential
strength and high-grade nature of the mineralized system in the area.
Drilling is planned in the Porco area and on Mina Casiterita commencing in February 2023 with
geological mapping, sampling and geophysical surveys now in progress on the full land package
across the Iska Iska region.
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About Eloro Resources Ltd.
Eloro is an exploration and mine development company with a portfolio of gold and base-metal
properties in Bolivia, Peru and Quebec. Through its Bolivian subsidiary, Eloro has an option to acquire
a 100% interest in the highly prospective Iska Iska Property, which can be classified as a
polymetallic epithermal-porphyry complex, a significant mineral deposit type in the Potosi
Department, in southern Bolivia. A recent NI 43-101 Technical Report on Iska Iska, which was
completed by Micon International Limited, is available on Eloro’s website and under its filings on
SEDAR. Iska Iska is a road-accessible, royalty-free property. Eloro also owns an 82% interest in
the La Victoria Gold/Silver Project, located in the North-Central Mineral Belt of Peru some 50 km
south of Barrick’s Lagunas Norte Gold Mine and Pan American Silver’s La Arena Gold Mine.
.
For further information please contact either Thomas G. Larsen, Chairman and CEO or
Jorge Estepa, Vice-President at (416) 868-9168.
Information in this news release may contain forward-look ing information. Statements containing forward looking
information express, as at the date of this news release, the Company’s plans, estimates, forecasts, projections,
expectations, or beliefs as to future events or results and are believed to be reasonable based on information currently
available to the Company. There can be no assurance that forward-looking statements will prove to be accurate. Actual
results and future events could differ materially from those anticipated in such statements. Readers should not place
undue reliance on forward-looking information.
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