Modern Mining: Featured News

The new Mako gold mine of Toro Gold in eastern Senegal is off to a good start, with most metrics exceeding forecasts. Mill throughput for the first three months of operation, for example, was 540 kt at 2,34 g/t Au versus the budget of 460 kt at 2,49 g/t Au while average cash costs (including the ramp up phase) were US$746/oz versus the budget of US$984/oz, excluding royalties.

Mako Plant

The 1,8 Mt/a processing plant of the Mako gold mine (photo: Mako).

Construction of Mako, which is 90  % owned by Toro, a Guernsey-registered private gold exploration and development company, started in August 2016 and the first gold pour took place on 26 January this year. Built within its budgeted capex of US$158 million, it will produce 136 koz/a of gold over six years of open-pit operation (although eight years of processing are planned). The ore is treated in a 1,8 Mt/a processing facility built by Lycopodium.

Highlights over the period January to April 2018 include a successful transition to steady state operations at design levels of performance within a month of first gold pour; gold sales of 32 556 ounces at US$1 325/oz, slightly ahead of the 32 270 oz target; and metallurgical recoveries of 94,8 % against the forecast of 91,3 %.

Following on from the first gold pour at the end of January, the mine completed a series of operational trials over a 7-day continuous period to confirm operational performance of the metallurgical plant and ensure its ability to meet and maintain design parameters – the Performance Trial.

The ore types at Mako are hard and abrasive and a key focus of the Performance Trial was to therefore ensure the comminution circuit could achieve the target grind size at forecast power consumption and circuit wear rates/consumable use. Mining operations had encountered significantly more ‘weathered/soft’ full grade ore in the pit than expected leading to the likelihood that the trial would be based on non-representative softer ore.

Management accordingly took the decision to utilise available lower grade hard/fresh ore for the trial which led to feed grades over the trial period of 1,7 g/t Au versus a budgeted grade for the period of 2,5 g/t Au. This led to a lower than planned average mill feed grade over the period, although this has been offset by higher than expected mill throughput. Following the Performance Trial, the run of mine ore being fed to the mill is in line with budget forecasts.

The Performance Trial was successfully completed during February 2018 and the construction team demobilised from the mine site shortly thereafter.

Mining operations have been on-going since mid-2017 during the construction phase and have progressed well with good performance from the mining contractor African Mining Services Senegal SARL (AMSS).

Grade control reconciliation to date, says Toro, shows good correlation with the forecast reserve model with grade.

Given the topography of the deposit, the mining plan developed as part of the feasibility study anticipated very limited weathered/soft material to be mined with hard/fresh ore anticipated almost from the start of mining operations. During the development of the open pit, however, it became apparent that the weathering profile was more extensive than expected resulting in both the availability of free dig material and the use of lower powder factors for blasting – leading to improved operating costs through a reduction in drill and blast costs.

A strategic review of the pit sequencing and access layout is underway with the aim of optimising operational flexibility and reducing operating costs through shorter haulage distances. In the short term, there has been a focus on developing available ore benches over the first quarter with mining operations switching focus back to waste stripping during Q2 2018. To this end, ore tonnes mined are 10 % higher than budgeted over this period against waste production which is 18 % lower than forecast – this short term change has been implemented without impacting on the availability of mill feed during the balance of 2018 and beyond.

Commissioning and ramp up of the processing plant has been excellent, says Toro, with steady state production at nameplate levels experienced from within a month of the first gold pour. Accordingly, year to date milling is some 18 % above forecast as a result of both the rapid ramp up and mill availability of 95,4 % over the period against the forecast 94 %. Further, despite this increase in throughput, the plant is achieving its target grind size of P(80) 125 μm while using approximately 6,5 MW of power against the design of 8,4 MW.

General observations of wear points throughout the comminution circuit indicate better than forecast liner life which has led to lower operating costs and higher availability of the plant, reports Toro.

The fixed tail grade is some 44 % lower than forecast, leading to improved metallurgical recoveries with the year to date indicating a recovery of 94,8 % over the period against a budget of 91,3 % recovery.

Further optimisation of the process plant will occur over the next six months to determine the optimal performance of the facility with target grind size, reagent use and throughput rates/power consumption reviewed with the aim of improving gold production and reducing costs.

Total employment at the mine during April, inclusive of all sub-contractors, was some 754 people. Training and skills development of the local Senegalese workforce remains a focus to ensure that the mine continues to provide the maximum long-term benefit to both the local and national economy of Senegal.

Toro says that management focus for the rest of 2018 will be to identify further optimisation opportunities to improve the already excellent operating parameters. A review of the open-pit mining schedule and haulage routes, powder factors and reserve calculations will be completed in parallel with a review of plant performance which will look at throughput and grind size trade-offs to determine an optimal new life of mine plan during the second half of 2018. This is expected to be based on an updated resource model that will likely include the results of on-going exploration works on the main deposit.

Comments Martin Horgan, Toro’s CEO: “After a highly successful construction period, the transition to operations has gone extremely well with all aspects of the mine operating either in line or better than forecast. Adrian de Freitas, General Manager, and the whole operations team have delivered an excellent first set of results and it has been achieved safely with no LTIs recorded for the period. I am also delighted to note that of the total workforce 88 % are Senegalese and over 60 % are employed from the local Kedougou region.”

Contact Modern Mining

Title: Editor
Name: Arthur Tassell
Email: mining@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

Title: Advertising Manager
Name: Bennie Venter
Email: benniev@crown.co.za
Phone: +27 11 622-4770
Fax: +27 11 615-6108

BANNER 9

 
Full Name*
Invalid Input

Company Name*
Invalid Input

Your Email*
Invalid Input

Phone*
Invalid Input

Postal Address 1*
Invalid Input

Postal Address 2*
Invalid Input

Postal Code*
Invalid Input

Street Address 1
Invalid Input

Street Address 2
Invalid Input

Postal Code
Invalid Input

Town / City*
Invalid Input

Country*
Invalid Input

Magazine

Invalid Input

Invalid Input