02:45:43 EST Sat 02 Mar 2024
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Altamira Gold Corp
Symbol ALTA
Shares Issued 211,527,286
Close 2024-02-06 C$ 0.16
Market Cap C$ 33,844,366
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Altamira met tests recover 88.2% Au at Maria Bonita

2024-02-07 11:48 ET - News Release

Mr. Mike Bennett reports


Altamira Gold Corp. has released the results of initial column leach tests on mineralized drill core from the Maria Bonita gold discovery.


  • 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 per cent for a feed size of 100 per cent passing 9.5 millimetres.
  • The Maria Bonita bedrock or primary mineralization has a broad halo of oxidized saprolite material containing gold associated with the intrusive-hosted and disseminated bedrock mineralization. A coherent, gold-mineralized saprolite zone, defined by a 0.4 g/t (gram per tonne) gold-in-soil contour, extends over an area of approximately 320 metres by 270 metres (approximately nine hectares).
  • To date, both diamond and auger drilling define the thickness of the saprolite as between four and 17 m.
  • The company intends to conduct further tests to optimize the leach dynamics and scope a potential fast-track, low-cost, initial operation to mine the mineralized saprolite.

Chief executive officer Mike Bennett commented: "Following the earlier excellent results from initial agitated tank leach metallurgical test work, where over 90-per-cent 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 cash flow."

Consulting metallurgist Ian Gordon Hall Dun, BSc (engineering), 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 optimize the crush size and conditioning of the feed to further improve the kinetics and potential economics."

Cajueiro project

The Cajueiro project is located approximately 75 kilometres northwest of the town of Alta Floresta in the state of Mato Grosso in western-central 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.

The Cajueiro project has current National Instrument 43-101 resources of 5.66 million tonnes at 1.02 g/t gold for a total of 185,000 ounces in the indicated resource category and 12.66 Mt at 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 69 m at one g/t gold in MBA005, 50 m at 1.1 g/t gold in MBA004, 55 m at one g/t gold in MBA002, 50 m at one g/t gold in MBA001 and 45 m at 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 program of approximately 5,000 metres is under way 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 2, 2023, and April 12, 2023, using both cyanide and thiosulphate leaching agents, respectively, which were very positive and resulted in over 90-per-cent gold recoveries.

For the current test, samples of approximately 30 kilograms were prepared from composited quarter core subsamples of the initial diamond drilling program (holes MBA001 to MBA005). The samples were composited from up to 42 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, Mr. Dun, BSc (engineering), MSc.

Samples were first crushed to 80 per cent passing 9.5 mm. Head grades analyzed in the laboratory were broadly in line with the estimated grades from the calculated drill core composite assay grades. The saprolite sample received by the laboratory contained 14 per cent 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 two kg/tonne of cement and lime to facilitate both a pH of 10.5 to 11 and percolation through the column over the life of the leach test. Laboratory columns of one m height and six inches diameter were used. The percolation rate was 10 litres per hour per square metre of surface area. Cyanide concentrations of 300 to 500 parts per million were used. The columns were irrigated for 30 to 45 days.

The results show a net gold recovery of 88.2 per cent with a cyanide consumption of 750 g/t for saprolite. This is a very positive result for a coarse 9.5 mm 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 optimize 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. The agitated leach test for the saprolite reported a gold recovery of 91.6 per cent at a cyanide consumption of 330 g/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 optimized.

Column leach testing of the fresh rock material gave an initial gold recovery of 51.8 per cent. 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-per-cent 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 program. 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 5.35 million stock options to directors, officers, employees and consultants of the company. The stock options are exercisable for a term of five years at an exercise price of 16 cents per common share. The options are subject to the company's stock option plan.

Qualified person

Guillermo Hughes, FAIG and MAusIMM, 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 six projects, comprising approximately 190,000 hectares, within the prolific Juruena gold belt which historically produced an estimated seven Moz to 10 Moz of placer gold. The company's advanced Cajueiro project has NI 43-101 resources of 5.66 Mt at 1.02 g/t gold for a total of 185,000 oz in the indicated resource category and 12.66 Mt at 1.26 g/t gold for a total of 515,000 oz in the inferred resource category.

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