Altamira Gold Reports 92% Gold Recovery from Metallurgical Tests Using the Alternative Clean Mining Thiosulphate Leach Technique on Drill Samples from the Maria Bonita Target, Cajueiro Project, Brazil

April 12, 2023 7:30 AM EDT | Source: Altamira Gold Corp.

Vancouver, British Columbia--(Newsfile Corp. - April 12, 2023) -  Altamira Gold Corp. (TSXV: ALTA) (FSE: T6UP) (OTC Pink: EQTRF), ("Altamira" or the "Company") is pleased to announce that it has received the results of an initial metallurgical leach characterisation test on a drill core composite sample of primary mineralization from the recent Maria Bonita discovery within the Cajueiro project in Para state, Brazil.

This test complements those test results released on March 1, 2023, using the conventional cyanide leach technology. The current test was conducted at SGS Australia and CSIRO laboratories in Western Australia using a proprietary thiosulphate leach technique developed by Clean Mining, a subsidiary of Clean Earth Technologies (CET), based in Singapore. CET is commercialising a non-cyanide approach to leaching of gold ores that was originally developed in Australia by CSIRO. Cyanide leaching is the traditional method to extract low grade gold. Thiosulphate leaching offers a more environmentally benign route to gold extraction.


  • A 24-hour agitated leach test using the thiosulphate leach agent, at a grind size of 80% passing 75µm, recovered 92% of total gold content.
  • The head grade of the sample treated compares well with the original assays of the diamond drill composites making up the sample (50g fire assays). The original assays from the drill samples gave 1.07g/t gold. The Clean Mining laboratory head grade (500g sample) gave 1.04g/t gold. The Clean Mining leach test resulted in a back-calculated head grade of the sample (after leaching) of 1.10g/t gold (1000g of leach test sample). These results underline the consistency of the mineralization.
  • A cyanide leach test was also conducted in parallel using the same grind and leach time and yielded a gold recovery of 91%. These results correlate very well with recently announced cyanide leach tests carried out in the Testwork laboratory in Brazil, which also returned an average cyanide leach gold recovery of 91% for primary mineralized material from Maria Bonita.
  • Final drill results from a series of reconnaissance drill holes completed during 2022 at the Santa Helena project returned several notable intercepts including 0.8m @ 44.8 g/t gold and 0.9m @ 10.4 g/t gold.

Altamira Gold President and CEO, Michael Bennett, commented; "We are pleased to receive this very positive result, which underlines the potential for a non-cyanide process route to be technically highly competitive with conventional cyanide leaching at our Cajueiro project. Our previous work with Clean Mining on oxide material from the existing Cajueiro resources, gave similar highly encouraging results, and we have now achieved high recoveries with primary material from the new Maria Bonita discovery. This initial test creates a strong option to now evaluate the application of both the Clean Mining and conventional cyanide leach technologies to a start-up heap leach project."

Consulting metallurgist Ian Gordon Hall Dun BSc (Eng), MSc., who has 45 years of experience as a metallurgist in Brazil, observed, "This leach test supports the concept of Altamira utilising a non-cyanide route to gold recovery for the Maria Bonita project. At this initial stage, the results provide higher gold recoveries than conventional cyanide leach at low reagent consumption rates which is a very positive initial result. We will further develop this option through testing both the Clean Mining and conventional cyanide leach routes for heap leaching conditions".


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).

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Figure 1: Location of the Cajueiro, Apiacas and Santa Helena projects.

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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.

Several strong mainly untested gold-in-soil anomalies occur within a short radius of the Cajueiro resource area and include Maria Bonita, Sossego and Novo Sonho (Figure 2). Maria Bonita is the strongest of these peripheral gold-in-soil anomalies and is open to the west, with the current footprint of the geochemical anomaly covering an area comparable in size to the entire Cajueiro mineral resource area.

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Figure 2: Location of the Cajueiro (Baldo) mineral resource and the Maria Bonita target showing relative size and intensity of the soil responses. The Maria Bonita soil anomaly remains open to the west and north.

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Maria Bonita Target

The Maria Bonita target is located approximately 7km northwest of the Cajueiro resource area (Figure 2) and is defined by a gold-in-soil anomaly which is at least 800 x 800m in size and open to the west. The central part of the anomaly returned gold values in excess of 1g/t gold in soils (Figure 3).

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Figure 3: Gold-in-soil values at the Maria Bonita target over background aero-magnetic data (derivative of total magnetic intensity - TMI) with structural interpretation.

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Maria Bonita Metallurgical results

Following completion of holes MBA001-MBA004 (see press releases dated September 7 and November 16, 2022), a representative composite sample of fresh rock mineralization was prepared from assay sample coarse rejects, returned from the analytical laboratory. The sample weighed 5kg and was comprised of 15 subsamples of individual core intervals, each of which measured 0.77-1.5m.

The samples were submitted to Clean Mining and the testwork was conducted at SGS Australia and CSIRO laboratories in Western Australia from January to February 2023.

Clean Earth Technologies (CET) is a Singapore-based EnviroTech company that focuses on the identification, development, and commercialization of research for non-toxic, environmentally friendly industry processes and remediation. CET has two patented technologies, a nontoxic leach reagent and a resin-based collector.

The testwork programme involved crushing and grinding the sample to 80% passing 75 microns. Standard bottle roll leach tests were conducted using 1000 g of sample repulped to 40% solids, with pH adjusted to 5-7 for Clean Mining's reagent and 10.8 for a comparable cyanide leach test.

For the Clean Mining leach test, 31.2 grams of clean leach reagent (CLR), equivalent to 20 grams of reagent per litre of liquor) and 5.6 grams of clean leach enhancer (CLE) equivalent to 3.7 grams of reagent per litre of liquor were added. The concentration of reagents and the pH were monitored for the duration of the test. After 48 hours of leaching, the pulp was filtered and washed with three displacements of water.

The results indicate a consumption of 3.59 kg/t of CLR and 0.36 kg/t of CLE and an average gold recovery of 92.1% within 24 hours. As concluded by Clean Mining, "The ore has shown low reagent consumption, high gold recovery and fast leaching kinetics".

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Figure 4: Progressive leach recovery of gold using CET and conventional cyanide leach reagents.

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For the comparable cyanide leach, gold recovery after 24 hours leaching was 91% with a sodium cyanide (NaCN) consumption of 0.3 kg/t.

When compared with the prior results for metallurgical characterisation for Maria Bonita mineralization, the thiosulphate leach gave high recoveries, marginally higher than those for conventional cyanide leaching.

Au recovery %Reported 01/03/23 This report
Fresh Rock 89.990.592.391.1
CN = conventional cyanide leach
CET = Clean Earth Technologies thiosulphate leach

Table 1: Summary for leach test results for Maria Bonita project.

As a next step, the Company plans to further investigate crushing and grinding characteristics, the amenability of both conventional cyanide and thiosulphate leach to the dynamics to heap leaching, and further evaluation of agitated leach using both reagent options.


The Santa Helena project is located immediately adjacent to the paved BR-163 federal highway in the state of Mato Grosso and 60km SW of the Jaca porphyry copper deposit which was recently discovered by Anglo American Corporation (Figure 1).

Previous artisanal mining activity has focused on high-grade gold hosted in vein structures. However, mapping, soil and rock chip sampling by Altamira has identified both extensions to the known vein gold targets plus significant copper, molybdenum and gold anomalies in soils related to areas of porphyry-style alteration in a zone which extends 7km E-W by 4 km N-S, indicating the presence of a very large hydrothermal system.

Santa Helena Drill results

Twenty-three diamond drillholes totalling 3,615m were completed on eight separate targets identified by a combination of soil sampling, geological mapping, and reviews of artisanal miners' workings. The Santa Helena area contains several active artisanal workings extracting gold from discrete vein and shear structures. Altamira's prospecting work identified both gold and copper-in-soil targets. The initial scout drilling reported here relates to the gold targets, all of which are the site of minor to significant former or current artisanal workings.

Notable drill results received from the scout drilling program are shown in Table 1. Highlights include 0.8m @ 44.8 g/t gold from the Dorival Sul target and 0.9m @ 10.4 g/t gold and 9.2m @ 1.2 g/t gold from the Tucura target.

Target  Hole Depth From To Metres g/t Au
Gabriel  DDSTH0003 341 174 177 3 0.47
Gabriel  DDSTH0009 129.96 4.8 23 18.2 0.36
Gabriel  DDSTH0012 151.47 70.55 71.55 1 0.45
Flecha Dourada DDSTH0013 142.42 44 46.5 2.5 3.64
Flecha Dourada DDSTH0014 106.53 31 32 1 1.02
Tucura  DDSTH0015 167.73 92.3 92.8 0.5 1.74
Tucura  DDSTH0016 139.74 57.2 58.1 0.9 10.38
Dorival Sul DDSTH0017 134.35 92 92.8 0.8 44.8
Dorival Sul DDSTH0018 79.68 63.9 65.4 1.5 3.10
Tucura  DDSTH0020 226.01 173.8 183 9.2 1.17
Tucura  DDSTH0021 151.56 56 58 2 0.50

Table 2: Santa Helena significant drill results.

Several coherent copper targets remain to be tested at Santa Helena, pending the completion of geophysical surveys, which are now planned for Q2 2023.

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 projects within western central Brazil. The Company holds 8 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.

On Behalf of the Board of Directors,


"Michael Bennett"

Michael Bennett
President & CEO

Tel: 604.676.5660

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.


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.

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