Tesoro Resources reveals up to 99% gold recoveries from El Zorro testwork

Tesoro Resources ASX TSO El Zorro Metallurgical Testwork Results gold Chile
Metallurgical testwork shows ore from the Ternera gold deposit is amenable to conventional gravity and CIL processing methods.

Gold explorer Tesoro Resources (ASX: TSO) has announced positive initial metallurgical testwork results from its El Zorro gold project in Chile, indicating gold recoveries of up to 99%.

The testwork was conducted on a 50kg sample of mineralised, fresh rock material taken from four drill holes at the project’s Ternera deposit.

Channel sampling and a recently completed phase one drilling campaign at Ternera has recovered wide zones of high-grade gold, with mineralisation confirmed from surface to depths of more than 150m.

In an announcement today, the explorer said the initial testwork results indicate the Ternera material is free milling, with a high gravity recovered gold component and excellent cyanide leaching characteristics.

“The high gravity and cyanide leach recoveries achieved in this work support the potential for processing of material from Ternera using conventional gravity and cyanide-in-leach processes at a relatively coarse grind size,” Tesoro managing director Zeff Reeves said.

“This work will enable the development of a detailed metallurgical testwork program to fully define the project flowsheet and continue to progress the project toward development,” he added.

Testwork results

The metallurgical testwork, including cyanide leach tests, gravity recovery and determination of bond work index (hardness) testing, was conducted by ALS Laboratories in Perth, Western Australia with the results reviewed and interpreted by Mintrex.

The 50kg fresh rock sample returned a calculated head grade of 2.39 grams per tonne of gold and low levels of base metals.

During gravity recovery testing, the sample was ground to several size fractions from 850 micrometres down to 75µm with the results showing the ore is very amenable to gravity concentration and ideally up to 76% of the gold ground to 75µm can report to the gravity circuit.

Leaching of the tails at different grind sizes recovered another 25.5-29.5% of the gold for overall gold extractions of 94.9% (at 250μm), 98.3 % (at 106μm) and 98.8% (at 75μm).

Next steps

Tesoro said it plans to implement recommendations provided by testwork reviewer Mintrex for a detailed metallurgical testwork program to test both transitional and fresh ore types of high and low gold grade domains.

This program will comprise comminution (including high pressure grinding roll), gravity, grind establishment and leaching characteristics to provide detailed inputs for future plant design during scoping or feasibility studies, the company reported.

Tesoro is planning to begin this work during the fourth quarter of 2020.

Meanwhile, the company has planned a second phase of drilling due to begin in July. This program will focus on infill and extensional drilling at Ternera to advance the project towards a maiden resource estimate.

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