Eloro Resources Provides Update on the Preliminary Metallurgical Testwork Program for the Iska Iska Silver-Tin Polymetallic Project, Potosi Department, Bolivia

June 13, 2022

TORONTO, June 13, 2022 (GLOBE NEWSWIRE) -- Eloro Resources Ltd. (TSX-V: ELO; OTCQX: ELRRF; FSE: P2QM) (“Eloro”, or the “Company”) is pleased to provide an update on its preliminary metallurgical testwork program for the Iska Iska silver-tin polymetallic project in the Potosi Department, southern Bolivia. The work program including testwork for development of a preliminary metallurgical flowsheet and preliminary mineralogical characterization, is being carried out by Blue Coast Research Ltd. (“Blue Coast”) based in Parksville, BC. The objective is to develop the preliminary flotation flowsheet to maximize lead, zinc and precious metals into saleable concentrates in the Santa Barbara polymetallic deposit and to develop a preliminary flowsheet for tin in both the Santa Barbara and the deeper tin-dominant mineralization.

Blue Coast has world-class metallurgical testing, analytical services, flowsheet development, consulting, and operational support. Their excellent team has been augmented with the addition of Mr. Mike Hallewell, C.Eng., a senior independent mineral processing consultant based in Cornwall, England, who has extensive specialist knowledge in the recovery of tin at mining operations and exploration projects worldwide.

The metallurgical testing is being directed by Richard Gowans, P.Eng., Principal Metallurgist for Micon International Limited, who is an independent Qualified Person as defined under NI 43-101.

Tom Larsen, CEO of Eloro, commented: “The metallurgical testing program at Blue Coast is progressing well. The initial focus of their work was on the Santa Barbara polymetallic mineralization for Ag, Zn and Pb recovery based on samples from discovery hole DHK15 and hole DHK-18. The tin-rich zone in hole DSB-06 was also selected for testing but at that time it was uncertain how this mineralization was connected to the Santa Barbara polymetallic deposit. However, with further drilling and solid work by our geological and geophysical team, we now know that there is extensive tin mineralization at depth beneath the polymetallic mineralization. Once testing is completed on DSB-06, we will be adding additional samples from tin-rich holes to enable further development of an appropriate flow sheet for tin. While arsenic and other potentially deleterious elements are being tracked during the testwork program, these are not anticipated to be a material issue at the levels in current tests.”

Metallurgical Samples

The samples used for the preliminary program completed to date comprise three representative metallurgical samples from existing drill core. The initial three composites are:

  • Composite drill hole DHK-15, from 131 m to 198 m, mineralized breccia.
  • Composite drill hole DHK-18, from 76 m to 140 m, mineralized dacitic envelope.
  • Composite drill hole DSB-06, from 413 m to 477 m, tin-rich mineralized zone.

Approximately 60 m of quarter-core from each drill hole was selected for these three metallurgical composite samples. The head analyses for these three composites are presented in Table 1. It is noted that the arsenic (As) grade is relatively low, being less than = 0.03% for all the three composite samples. Although not anticipated to be a material issue at these levels, the As and other potentially deleterious elements will be tracked during the testwork program.

Table 1: - Metallurgical Sample Head Analyses

Sample ID

Note: ppm = grams per tonne (g/t)

The initial testwork completed by Blue Coast at the end of May 2022 included preliminary mineralogical characterization studies, open circuit sulphide flotation scoping tests and locked cycle flotation tests using composites DHK-15 and 18. The work conducted on DHK-15 and 18 factored into consideration the preliminary test work conducted by the Universidad Técnica de Oruro on different samples.

The DSB-06 sample is extracted from deeper higher-grade tin mineralization that is seen to replace the polymetallic lead-zinc-silver-tin mineralization type at depth and this sample has become the subsequent focus of the ongoing tin studies at Blue Coast. Additional tin-rich samples will be added for further testing after the initial test program is completed.

Mineralogical Characterization of Metallurgical Composites

The Iska Iska composites DHK-15, DHK-18 and DSB-06 were analyzed using the TESCAN Integrated Mineral Analyzer (TIMA), a fully automated analytical scanning electron microscope, to measure bulk mineralogy, sulphide grain size and liberation to support the metallurgical test program. In addition, a suite of electron microprobe analyses was completed on various sulphide and oxide species to better understand overall mineral chemistry and tin deportment.

Sulphide minerals in base metal composites DHK-15 and DHK-18 consisted of mainly sphalerite, galena and pyrite. Sulphide mineral liberation was very good at the test grind of 80% passing (P80) 70 microns and flotation testwork, described below, was able to achieve good lead-zinc separation. Non-sulphide gangue minerals in all composites consisted of quartz, various phyllosilicate minerals including micas, chlorite and kaolinite, and minor Fe oxides.

Cassiterite (a tin oxide mineral) was the dominant tin mineral identified in tin composite DSB-06. Cassiterite was moderately liberated (69% of grains had liberation of 80% or better at the test grind of P80 70 microns). Cassiterite formed middling particles with pyrite, rutile, quartz and iron oxides. Pyrite in DBS-06 was well liberated. Initial flotation testwork, described below, focused on separating pyrite from the cassiterite.

Microprobe analyses were completed on a group of pyrite, sphalerite, galena and cassiterite grains in the metallurgical composites. Tin was identified in trace amounts within the structure of galena and sphalerite in the base metal composites, suggesting that the sulphide concentrates will contain a small amount of tin.

Geometallurgical Characterization

Separate to the testing of the metallurgical composites, a program of integrated mineralogical analysis is underway on a series of core slabs from Hole DSBU-03. This hole (see press release dated March 1, 2022) intersects both base metal and tin mineralization and is being used to develop a strong mineral reference library for the resource. The slabs have received hyperspectral (SWIR/VNIR), XRF and RGB scanning by GeologicAI and are now being prepared for petrographic analysis using TIMA and microXRF mapping. The combined data set will be used as a reference library to support the on-site automated core scanning program.

Lead-Zinc-Silver Flotation

Following a series of batch rougher and cleaner tests where the preliminary flotation circuit was developed, locked cycle tests (LCT) were completed using DHK-15 and DHK-18. A locked cycle flotation test is a series of identical batch flotation tests where recycled material from the previous cycle is added to the appropriate location in the flowsheet in the current cycle. The LCT is a standard method used to simulate continuous operating conditions.

The lead-zinc sequential flowsheet used for the LCTs included primary grinding followed by lead rougher flotation, lead rougher concentrate regrinding and 3 stages of lead cleaner. The lead rougher tailings and lead first cleaner tailings fed the zinc rougher stage, and similar to the lead circuit, the flowsheet included regrinding of zinc rougher concentrate followed by three zinc cleaner stages. The final residue streams were the zinc rougher tailings and zinc first cleaner tailings.

Each LCT comprised 6 cycles where the final cycles were deemed to be relatively stable and the circuit appeared to reach equilibrium. Summaries of the average results from the last 3 cycles for both tests are presented in Tables 2 and 3.

Table 2: Summary of Locked Cycle Test Average Results for Sample DHK-15

Wt. %
Assays% Distribution
Pb Cl.3 Conc.2.0104756.77.378.8422.668.
Zn Cl.3 Conc.4.31861.5849.610.934.326.55.387.116.643.4
Zn Cl.1 Tail5.2230.581.1619.821.
Zn Ro. Tail88.600.080.131.300.401.45.54.540.910.5
Calc. Head100.0301.282.452.833.39100.0100.0100.0100.0100.0

The LCT DHK-15 lead recovery into the final lead concentrate grading 56.7% Pb was 86.9% while the silver grade was 1,047 g/t. The zinc recovery into a final zinc concentrate containing 49.6% Zn was 87.1%. The total silver recovery was 94.6%, including 68.1% and 26.5% into the lead and zinc concentrates, respectively.

Table 3: Summary of Locked Cycle Test Average Results for Sample DHK-18

Wt. %
Assays% Distribution
Pb Cl.3 Conc.1.4105756.27.105.4018.943.572.
Zn Cl.3 Conc.5.02581.4051.48.2732.037.66.486.912.035.2
Zn Cl.1 Tail9.6391.001.3611.711.910.98.74.432.425.1
Zn Ro. Tail84.
Calc. Head100.0341.102.963.474.56100.0100.0100.0100.0100.0

The lead recovery for LCT DHK-18 into the final lead concentrate grading 56.2% Pb was 72.2% while the silver grade was 1,057 g/t. The zinc recovery into a final zinc concentrate containing 51.4% zinc was 86.9%. The silver recovery totalled 81.0%, including 43.5% and 37.6% into the lead and zinc concentrates, respectively.

Samples of final concentrate products from each LCT have been submitted for multi-element analyses to assess the distribution of other potential valuable or deleterious components.

The preliminary flotation test results are very encouraging. The results received so far for drill hole sample DHK-15 are considered very good with high lead, zinc and silver recoveries, and although sample DHK-18 results were not quite as good for lead, zinc recovery was high and overall silver distribution into the final products was good.

Acceptable separate lead and zinc concentrates containing significant payable silver that adds considerable value to these products have been produced from both samples. Work will continue at Blue Coast and other metallurgical laboratories to fine tune the flotation conditions to maximize metal recoveries and quality of concentrates produced.

Tin Metallurgy

DSB-06 tin-rich sample contains low levels of lead, zinc and silver-bearing sulphides, the main sulphide mineral present in this sample being pyrite. No stannite (a tin sulphide mineral) is present in this sample; the tin mineralisation consists entirely of cassiterite.

The pyrite to cassiterite ratio in DSB-06 is circa 5:1. The Blue Coast approach has been initially focused on removing the pyrite prior to traditional beneficiation methods of cassiterite that are employed, using gravity followed by tin flotation. The pyrite is well liberated across all size fractions tested and therefore, the preliminary bulk sulphide flotation sulphur recoveries were good.

A preliminary study has identified that grinding the sample generates predominantly fine cassiterite grains that are more amenable to tin flotation technology. Staged comminution options will be considered to minimise fine cassiterite production in conjunction with staged gravity recovery of whatever coarse grained cassiterite is present and recoverable at, as early a stage in the process as possible.

Gravity release analysis by size testwork on bulk sulphide flotation tailings is in progress to identify the amenability of the mineralization to gravity concentration.

One bulk sulphide rougher flotation test followed immediately by a rougher tin flotation test has been conducted using unoptimized conditions. The rougher tin flotation cassiterite stage recovery was encouraging suggesting that the mineralization will be amenable to tin flotation technology. Further mineralogical work is in progress on the tin flotation rougher concentrates produced to ascertain if this rougher concentrate contains predominantly free liberated cassiterite that would therefore be expected to be upgraded by cleaning. Tin flotation is a universally practised technology and used by all the major hard rock tin mines globally as a method of recovering cassiterite that is too fine grained for conventional gravity concentration.

The tin mineralogy and physical competence will be linked to geological attributes. This will become a key feature in contextualising any variances in these parameters across the deposit. The GeologicalAI scanner, which is now on site and will be operational shortly, and the geometallurgical work noted above, will be very important in characterizing the geological attributes.

The test work is too premature to quote tin recovery numbers, but the initial mineralogy shows that the tin minerals are all in the form of cassiterite with insignificant amounts of stannite. Furthermore, the preliminary testing indicates that tin flotation will be a key recovery route and the preliminary tin flotation test work results are encouraging.

Qualified Person

The metallurgical testing is being directed by Richard Gowans, P.Eng., Principal Metallurgist for Micon International Limited, who 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, 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 for 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. 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.

Eloro Resources at the PDAC

Eloro will be participating at the PDAC 2022 convention in Toronto and invites you to visit us at Booth IE3326 (Investors Exchange) in the South Building, Metro Toronto Convention Centre from June 13-15, 2022.

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. Eloro has an option to earn a 99% 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.

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 a target zone 1400m along strike, 500m wide and that extends to a depth of 600m. This zone is open along strike to the northwest and southeast as well as to the southwest. The Company’s nearer term objective is to outline a maiden NI 43-101 compliant mineral resource within this large target area. This work is advancing well with the mineral resource targeted to be completed in Q3 2022. Exploration drilling is also planned on other major targets in the Iska Iska Caldera Complex, including the Porco and Mina 2 areas.

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. Eloro has an option to acquire a 99% 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. Eloro commissioned a NI 43-101 Technical Report on Iska Iska, which was completed by Micon International Limited and 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. La Victoria consists of eight mining concessions and eight mining claims encompassing approximately 89 square kilometres. La Victoria has good infrastructure with access to road, water and electricity and is located at an altitude that ranges from 3,150 m to 4,400 m above sea level.

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-looking 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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