Altamira Gold Reports 88% Gold Recovery from Column Leach Tests on Mineralized Saprolite Material from the Maria Bonita Gold Discovery, Cajueiro Project, Brazil
Vancouver, British Columbia--(Newsfile Corp. - February 7, 2024) - Altamira Gold Corp. (TSXV: ALTA) (FSE: T6UP) (OTC Pink: EQTRF), ("Altamira" or the "Company") is pleased to announce the results of initial column leach tests on mineralized drill core from the Maria Bonita gold discovery.
Highlights:
Column leach metallurgical tests (simulating a heap leach) of a composite drill core sample of mineralized saprolite material from the Maria Bonita gold discovery at Cajueiro, returned an excellent gold recovery of 88% for a feed size of 100% passing 9.5mm
The Maria Bonita bedrock or primary mineralization has a broad halo of oxidised saprolite material containing gold associated with the intrusive-hosted and disseminated bedrock mineralization. A coherent, gold-mineralized saprolite zone, defined by a 0.4g/t gold-in-soil contour, extends over an area of approximately 320m by 270m (~9 hectares)
To date, both diamond and auger drilling define the thickness of the saprolite as between 4 and 17m.
The company intends to conduct further tests to optimise the leach dynamics and scope a potential fast track, low cost, initial operation to mine the mineralized saprolite.
CEO Mike Bennett commented; "Following the earlier excellent results from initial agitated tank leach metallurgical test work, where over 90% gold recovery was achieved, these new column leach test results indicate that the saprolite material at Maria Bonita should be highly amenable to heap leaching. Given the zero to very low strip-ratio over the central part of the mineralized area drilled to date, we now have a sound technical rationale to develop studies on a very low capital intensity start-up option on the saprolite mineralization. As we progress the current round of diamond drilling, we will further evaluate both the saprolite and underlying primary mineralization to identify options to generate early cashflow."
Consulting metallurgist Ian Gordon Hall Dun BSc (Eng), MSc., commented, "These column leach test results on saprolite are very encouraging as they offer very similar leach recoveries to those achieved to date for agitated leach. There is potential to optimise the crush size and conditioning of the feed to further improve the kinetics and potential economics."
CAJUEIRO PROJECT
The Cajueiro project is located approximately 75km NW of the town of Alta Floresta in the state of Mato Grosso (Figure 1) in central western Brazil and is easily accessible by road and has grid power. Cajueiro forms one of three key projects that Altamira controls in the region, the other two being Apiacas and Santa Helena (Figure1).
Figure 1: Location of the Cajueiro, Apiacas and Santa Helena projects.
The Cajueiro project has current NI 43-101 resources of 5.66Mt @ 1.02 g/t gold for a total of 185,000 oz in the Indicated Resource category and 12.66Mt @ 1.26 g/t gold for a total of 515,000 oz in the Inferred Resource category.
Maria Bonita Target
Prior diamond drilling returned excellent results from the initial nine diamond drill holes which include 69m @ 1g/t gold in MBA005, 50m @ 1.1 g/t gold in MBA004, 55m @ 1.0 g/t gold in MBA002, 50m @ 1.0 g/t gold in MBA001 and 45m @ 1.4 g/t gold in MBA003. Disseminated gold mineralization in the initial discovery holes is hosted within rhyolitic intrusive rocks. Importantly, although there is no outcrop in the discovery area, the mineralization is present from surface over most of the known mineralized zone to date.
A second diamond drill programme of approximately 5,000 metres is underway to test the anomalous magnetic and soil geochemistry footprint of the target. Holes MBA010 and MBA011 were completed during the month and samples are in the laboratory for analysis.
Maria Bonita column leach test results
The current column leach test results complement agitated leach test results released on March 2nd, 2023, and April 12th, 2023, using both cyanide and thiosulphate leaching agents respectively which were very positive and resulted in +90% gold recoveries.
For the current test, samples of approximately 30kg were prepared from composited quarter core subsamples of the initial diamond drilling program (holes MBA001-MBA005). The samples were composited from up to forty-two individual core samples, each generally representing a one metre interval of diamond drill core.
The samples were submitted to Testwork Desenvolvimento de Processo Ltda in Nova Lima, Minas Gerais, Brazil. The test work was conducted under the observation of the Company's consulting metallurgist, Ian Gordon Hall Dun BSc (Eng), MSc.
No of subsamples
Weighted avg grade g/t Au
Lab head grade g/t Au
Difference %
Saprolite
34
1.02
1.18
14%
Fresh rock
42
1.07
1.07
0%
Table 1: Estimated head grades (from weighted drill assay composites) versus average assayed head grades at the metallurgical laboratory
Samples were first crushed to 80% passing 9.5mm. Head grades analysed in the laboratory were broadly in line with the estimated grades from the calculated drill core composite assay grades (Table 1). The saprolite sample received by the laboratory contained 14% more gold than the estimated grade of the core composites making up the sample. This positive difference in the saprolite analysis might reflect the presence of physical gold within the saprolite. To date, visible gold has not been observed in the drill core however rare, fine physical gold has been observed from the panning of soils. This might represent upside for future bulk sampling of saprolite.
Each leach sample was agglomerated and conditioned using 2kg/t of cement and lime to facilitate both a pH of 10.5-11 and percolation through the column over the life of the leach test. Laboratory columns of 1m height and 6 inches diameter were used. The percolation rate was 10 litres per hour per square metre of surface area. Cyanide concentrations of 300-500ppm were used. The columns were irrigated for 30-45 days.
The results show a net gold recovery of 88.2% with a cyanide consumption of 750g/t for saprolite (Table 2). This is a very positive result for a coarse 9.5mm crush top-size, implying that the weathered saprolite is amenable to heap leaching and offering potential to further investigate crushing, agglomeration, and reagent dosing to further optimise the results.
In parallel, rolling bottle (agitated leach) control tests were conducted on samples ground to 80 per cent passing 200 mesh (75 microns) for 24 hours (Table 2). The agitated leach test for the saprolite reported a gold recovery of 91.6% at a cyanide consumption of 330g/t, confirming the previous tests conducted using a similar agitated leach methodology. This bottle roll test indicated that leach kinetics after 16 hours are similar to those for 24 hours, suggesting that agitated leach times can be optimised.
Column leach
Agitated leach
Au recovery %
CN consumption g/t
Au recovery %
CN consumption g/t
Saprolite
88.2
750
91.6
330
Fresh rock
51.8
1170
90.4
417
Table 2: Summary of results. CN is cyanide reagent.
Column leach testing of the fresh rock material gave an initial gold recovery of 51.8% (Table 2). Further work is warranted on finer crush and grind sizes to evaluate whether a suitable liberation and recovery combination for heap leaching versus the demonstrated agitated leach route (greater than 90% gold recovery) is likely to be economically attractive for the fresh rock material.
Further metallurgical testing to investigate crushing and grinding metrics, sample conditioning and reagent consumption is planned using drill core from the recently started second drill programme. In addition, shallow auger and diamond drilling will be used to supplement the drill database for the surficial saprolite gold deposit, leading to a mineral resource estimate.
Stock Options
Altamira also announces that it has granted 5,350,000 stock options to directors, officers, employees, and consultants of the Company. The stock options are exercisable for a term of 5 years at an exercise price of C$0.16 per common share. The options are subject to the Company's Stock Option Plan.
Qualified Person
Guillermo Hughes, FAIG and M AusIMM., a consultant to the Company as well as a Qualified Person as defined by National Instrument 43-101, supervised the preparation of the technical information in this news release.
About Altamira Gold Corp.
The Company is focused on the exploration and development of gold and copper projects within western central Brazil. The Company holds 6 projects comprising approximately 190,000 hectares, within the prolific Juruena gold belt which historically produced an estimated 7 to 10Moz of placer gold. The Company's advanced Cajueiro project has NI 43-101 resources of 5.66Mt @ 1.02 g/t gold for a total of 185,000 oz in the Indicated Resource category and 12.66Mt @ 1.26 g/t gold for a total of 515,000oz in the Inferred Resource category.
Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.
The securities described herein have not been registered under the U.S. Securities Act or any state securities laws, and may not be offered or sold in the United States absent registration or an applicable exemption from registration requirements under the U.S. Securities Act and any applicable state securities laws.
Forward-Looking Statements
Certain information contained herein constitutes "forward-looking information" under Canadian securities legislation. Forward-Looking information includes, but is not limited to, statements with respect to the extension of the Warrants. Generally, forward-looking information can be identified by the use of forward-looking terminology such as "will", "intends" or variations of such words and phrases or statements that certain actions, events or results "will" occur. Forward-Looking statements are based on the opinions and estimates of management as of the date such statements are made and they are subject to known and unknown risks, uncertainties and other factors that may cause the actual results to be materially different from those expressed or implied by such forward-looking statements or forward-looking information, including the receipt of all necessary regulatory approvals. Although management of the Company has attempted to identify important factors that could cause actual results to differ materially from those contained in forward-looking statements or forward-looking information, there may be other factors that cause results not to be as anticipated, estimated or intended. There can be no assurance that such statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements and forward-looking information. The Company will not update any forward-looking statements or forward-looking information that is incorporated by reference herein, except as required by applicable securities laws.
Notes
Gold analysis has been conducted by SGS method FAA505 (fire assay of 50g charge), with higher grade samples checked by FAA525. Analytical quality is monitored by certified references and blanks. Until dispatch, samples are stored under the supervision the Company's exploration office. The samples are couriered to the assay laboratory using a commercial contractor. Pulps are returned to the Company and archived. Drill holes results are quoted as down-hole length weighted intersections.
