OTTAWA, July 19, 2022 (GLOBE NEWSWIRE) —(“Cornerstone” or “the Company”) ( ; OTC:CTNXF; FWB:GWN1) is pleased to provide an update on its Bramaderos gold and copper joint venture in southern Ecuador (see Figures 1 and 2) in which it has a 12.5% interest carried by JV partner and project operator Sunstone Metals Ltd. (ASX: STM) through to the start of commercial production (see “About Bramaderos”, below).
Figures related to this news release can be seen in PDF format by accessing the version of this release on the Company’s website (www.cornerstoneresources.com) or by clicking on the link below:
- More strong assay results received from Brama for holes BMDD0019, and 027-032:
- 50.0m at 1.01g/t gold equivalent (AuEq1) (0.83g/t gold, 0.10% copper), from 102m in BMDD019
- 66.0m at 0.62 AuEq (0.45g/t gold and 0.09% copper), from 254m in BMDD027
- 72.0m at 0.55g/t AuEq (0.3g/t gold and0.14% copper), from 452m in BMDD028
- 72.7m at 0.68g/t AuEq (0.55g/t gold and 0.07% copper) from surface in BMDD029
- Results provide further indications that the Brama-Alba discovery is large by global measure and contains grades in line with many well-known porphyry projects
- Mineralization now outlined over 1.2km by 500m to >400m deep and remains open in all directions
- Highly positive initial metallurgical results: With a combined flotation and leach circuit, the results indicate that recoveries in excess of 86% for copper and 88% for gold can be achieved when targeting a saleable concentrate grade of above 20% copper
- Higher-grade zones close to surface, as shown by contouring of gold-equivalent domains
- The adjacent Melonal and Playas targets are emerging as highly promising prospects with strong potential to grow the size of Bramaderos; These two targets will be drilled this year
- Ongoing drilling with three rigs underpinning strong news flow over the remainder of 2022, culminating in a maiden resource estimate at Brama-Alba in the December quarter
Sunstone Managing Director, Malcolm Norris, said:
“We continue to increase the size of the Brama-Alba discovery with wide intersections with very good gold-copper grades from surface.
“We are also very pleased with the early metallurgical test work results. These results further strengthen the outlook for the maiden Mineral Resource Estimate this year. They also allow us to present results as gold-equivalent to better inform investors of the huge scale that we are developing at Brama-Alba and more broadly within the Bramaderos Project. The gold-equivalent data also allows for comparisons to more readily be made with other global porphyry systems where results are often reported as gold-equivalent and copper equivalent.
“Drilling is continuing with two rigs at Brama-Alba and one at Limon. The Brama-Alba drilling is filling in any gaps leading to the Resource and extending the scale of the system to the south-east and laterally. At the Alba end of the system, we are drilling holes that are discovering new areas of mineralization and we will continue to expand this zone to the west of hole BMDD007.
“At the eastern end of Brama, the deposit is plunging towards a significant magnetic body, which has not yet been drilled. This gives us reason to be optimistic in this area of further mineralization.
“It is also important to appreciate the outstanding location of Bramaderos, which is a key component to its value. The project is located immediately adjacent to the Pan American highway, and within reasonable distance of available hydroelectric power, supporting the economics of potential development opportunities. The project is also supported by nearby commercial airports and significant cities (Loja) and the project has strong community support. Ecuador sources 88% of its power from hydroelectricity and is ideally placed to participate in the global demand for clean energy sourced metals”.
* The reader is cautioned that there has been insufficient exploration to define a mineral resource at Bramaderos and it is uncertain if further exploration will result in the target being delineated as a mineral resource.
The results from all holes drilled at Brama-Alba show clearly that higher grade mineralization occurs in sub-domains within the larger 1.2km-long Brama-Alba system (Figures 3, 4, 5) and that these higher-grade domains cluster in the upper 400m (Figure 4).
The results provide more firm evidence that Brama hosts a substantial gold-copper porphyry system (Figures 3, 4, 5). There is also potential for this system to extend significantly to adjacent targets Melonal (west) and Playas (east) (Figure 6). These areas are expected to be drill tested in 2022.
Assay results for drill holes BMDD019, and 027 to 032 are provided in Table 1 below and shown in Figures 3, 4, and 5.
Gold equivalent results from all drill holes at Brama-Alba are shown in Table 2 (in the Figures) and clearly show the broad significant grades identified in this deposit.
Early-stage metallurgical test work completed on a range of mineralization styles from the Brama-Alba gold-copper porphyry deposit was undertaken by Base Metallurgical Laboratories in Kamloops, British Columbia and was managed by Brisbane-based specialist engineering consultancy group DRA Global.
Sighter metallurgical test work completed on the breccia and diorite lithologies, of the Alba and Brama deposits, yielded very encouraging results.
With a combined flotation and leach circuit, the results indicate that recoveries in excess of 86% for copper and 88% for gold can be achieved when targeting a saleable concentrate grade of above 20% copper.
Further test work, including alternative reagent and grind size regimes, will focus on improving recovery responses in a flotation-only circuit configuration to determine whether that configuration can be justified. Additional optimization testing of the current flotation-leach selection, to further improve recoveries, will also be conducted. Further details are provided below.
Table 1: Summary of mineralized intersections in Brama drill holes BMDD019, and BMDD027 – 032.
|Drill Hole||EOH (m)||From (m)||To (m)||Interval (m)||AuEq (g/t)||Au (g/t)||Cu (%)||Mo (ppm)||Ag (g/t)|
Measuring 4,948 hectares, the Bramaderos project is ideally located immediately adjacent to the Pan American highway, and within reasonable distance of available hydropower, supporting the economics of potential development opportunities. The project is supported by nearby commercial airports and significant cities (Loja) and enjoys strong community support.
The Bramaderos concession is owned by La Plata Minerales S.A. (“PLAMIN”), which in turn is owned 87.5% by Sunstone (the project operator) and 12.5% by Cornerstone.
Cornerstone’s 12.5% interest is carried by Sunstone through to the start of commercial production and repayable at Libor plus 2% out of 90% of Cornerstone’s share of earnings or dividends from the Bramaderos project (see news release 20-01 dated January 7, 2020).
More information about the property can be found at www.cornerstoneresources.com.
Yvan Crepeau, MBA, P.Geo., Cornerstone’s Vice President, Exploration and a qualified person in accordance with National Instrument 43-101, is responsible for supervising the exploration program at the Bramaderos project for Cornerstone and has reviewed and approved the information contained in this news release.
Sampling and Assaying
Surface and drill core samples from Brama were sent to the LAC y Asociados Cia. Ltda. Sample Preparation Facility in Cuenca, Ecuador for sample preparation. The standard sample preparation for drill core samples (Code PRP-910) is: Drying the sample, crushing to size fraction 70% <2mm and splitting the sample to a 1000g portion by riffle or Boyd rotary splitter. The 1000g sample is then pulverised to >85% passing 75 microns and then sent to the MSALABS in Langley, BC, Canada for gold and base metal analysis.
PLAMIN uses a fire assay gold technique for Au assays (FAS-111) and a four acid multi element technique (IMS-230) for a suite of 48 elements. FAS-111 involves Au by Fire Assay on a 30-gram aliquot, fusion and atomic absorption spectroscopy (AAS) at trace levels. IMS-230 is considered a near total 4 acid technique using a 0.25g aliquot followed by multi-element analysis by ICP-AES/MS at ultra-trace levels. This analysis technique is considered suitable for this style of mineralization.
Standards, blanks and duplicates are inserted ~1/28 samples. The values of the standards range from low to high grade and are considered appropriate to monitor performance of values near cut-off and near the mean grade of the deposit. The check sampling results are monitored and performance issues are communicated to the laboratory if necessary.
Sample security was managed through sealed individual samples and sealed bags of multiple samples for secure delivery to the laboratory by permanent staff of the joint venture. MSALABS is an internationally accredited laboratory that has all its internal procedures heavily scrutinized in order to maintain their accreditation. MSALABS is accredited to ISO/IEC 17025-2017 Accredited Methods and certified to ISO 9001-2015.
PLAMIN’s sampling techniques and data have been audited multiple times by independent mining consultants during various project assessments. These audits have concluded that the sampling techniques and data management are to industry standards. All historical data has been validated to the best degree possible and migrated into a database.
Rock samples are collected by PLAMIN’s personnel, placed in plastic bags, labeled and sealed, and stored in a secure place until delivery by PLAMIN employees to the LAC y Asociados ISO 9001-2015 certified sample preparation facility in Cuenca, Ecuador.
Rock samples are prepared crushing to 70% passing 2 mm (10 mesh), splitting 250 g and pulverizing to 85% passing 75 microns (200 mesh) (MSA code PRP-910). Prepared samples are then shipped to MSALABS, an ISO/IEC 17025-2017 Accredited Method company and ISO 9001-2015 laboratory in Langley, BC, Canada, where samples are assayed for a multi-element suite (MSA code IMS-136, 15.0 g split, Aqua Regia digestion, ICP-AES/MS finish) and gold by Fire Assay (MSA code FAS-111, 30 g fusion, AAS finish). Over limit results for Cu (>1%) are systematically re-assayed (MSA code ICF-6Cu, 0.2 g, 4-acid digestion, ICP-AES finish). Gold is assayed using a 30 g split, Fire Assay (FA) and AAS finish (MSA code FAS 111). Over limit results for Au (>10 g/t) are systematically re-assayed (MSA code FAS-415, FA, 30g., gravimetric finish).
Soil samples are dried at low temperature, screened to 80 mesh (MSA code PRP-757); a 15 grams portion is then assayed for a multi-elements suite (MSA code IMS-136, Aqua Regia digestion, ICP-AES/MS finish).
Quality Assurance / Quality Control (QA/QC)
MSALABS is a qualified assayer that performs and makes available internal assaying controls. Duplicates, certified blanks and standards are systematically used (1 control sample every 20-25 samples) as part of PLAMIN’s QA/QC program. Rejects, a 100 g pulp for each rock sample, are stored for future use and controls.
is a mineral exploration company with a diversified portfolio of projects in Ecuador and Chile, including the Cascabel gold-enriched copper porphyry joint venture in northwest Ecuador. Cornerstone has a 20.8% direct and indirect interest in Cascabel comprised of (i) a direct 15% interest in the project financed through to completion of a feasibility study and repayable at Libor plus 2% out of 90% of its share of the earnings or dividends from an operation at Cascabel, plus (ii) an indirect interest comprised of 6.85% of the shares of joint venture partner and project operator . Exploraciones Novomining S.A. (“ENSA”), an Ecuadoran company owned by SolGold and Cornerstone, holds 100% of the Cascabel concession. Subject to the satisfaction of certain conditions, including SolGold’s fully funding the project through to feasibility, will own 85% of the equity of ENSA and Cornerstone will own the remaining 15% of ENSA.
Further information is available on Cornerstone’s website: www.cornerstoneresources.com and on Twitter. For investor, corporate or media inquiries, please contact:
Mario Drolet; Email: [email protected]; Tel. (514) 904-1333
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This news release may contain ‘Forward-Looking Statements’ that involve risks and uncertainties, such as statements of Cornerstone’s beliefs, plans, objectives, strategies, intentions and expectations. The words “potential,” “anticipate,” “forecast,” “believe,” “estimate,” “intend”, “trends”, “indicate”, “expect,” “may,” “should,” “could”, “project,” “plan,” or the negative or other variations of these words and similar expressions are intended to be among the statements that identify ‘Forward-Looking Statements.’ Although Cornerstone believes that its expectations reflected in these ‘Forward-Looking Statements’ are reasonable, such statements may involve unknown risks, uncertainties and other factors disclosed in our regulatory filings, viewed on the SEDAR website at www.sedar.com. For us, uncertainties arise from the behaviour of financial and metals markets, predicting natural geological phenomena and from numerous other matters of national, regional, and global scale, including those of anti-mining sentiment in certain regions of Ecuador, or of an environmental, climatic, natural, political, economic, business, competitive, or regulatory nature. These uncertainties may cause our actual future results to be materially different than those expressed in our Forward-Looking Statements. Although Cornerstone believes the facts and information contained in this news release to be as correct and current as possible, Cornerstone does not warrant or make any representation as to the accuracy, validity or completeness of any facts or information contained herein and these statements should not be relied upon as representing its views after the date of this news release. While Cornerstone anticipates that subsequent events may cause its views to change, it expressly disclaims any obligation to update the Forward-Looking Statements contained herein except where outcomes have varied materially from the original statements.
On Behalf of the Board,
President and CEO
Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.
1 The equivalent calculation formula is AuEq(g/t) = Au(g/t) + Cu% x 1.77. The prices used were US$1,770/oz gold and US$9,750/t copper, and A$:US$0.70. Recoveries are estimated at 89% for gold and 86% for copper from preliminary metallurgical studies. In Sunstone’s opinion all the elements included in the metal equivalents calculation have reasonable potential to be recovered and sold.
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