Acacia Mining PLC (LON:ACA) today announced a mid-year Mineral Reserve and Mineral Resource update for its Gokona Mine at North Mara which adds to the long-term potential of this underground operation.
- Mineral Reserves as at end May 2019 increased by 13% in comparison to year-end 2018 from 1.117 million ounces (“Moz”) of gold at 5.6g/t to 1.257 Moz of gold at 5.5g/t; primarily driven by the successful additional drilling on the East and West extension at Gokona in Q4 2018 and Q1 2019, offset by mining depletion and a more conservative change in assumptions for crown pillar stope recovery.
- Measured and Indicated (“M&I”) Mineral Resources increased by 63% from 75,000 ounces (“Koz”) of gold at 3.3g/t to 122Koz of gold at 3.6g/t.
- Inferred Mineral Resources increased by 65% from 515Koz of gold at 6.5g/t to 849Koz of gold at 5.4g/t following the increase in drill density and confidence levels in the deeper areas of the deposit.
- All these increases are despite the fact that some 76Koz of gold have been mined in the intervening period.
Table 1: Summary Comparison between 31 May 2019 and 31 December 2018 Gokona Mineral Resources and Mineral Reserves
| 31 May 2019 * | 31 December 2018 | |||||||
| Tonnes (kt) | Grade (g/t) | Ounces (koz) | Tonnes (kt) | Grade (g/t) | Ounces (koz) | Change (koz) | ||
| Mineral Reserves | Proven | 960 | 6.04 | 188 | 1,386 | 5.86 | 261 | (73) |
| Probable | 6,100 | 5.45 | 1,069 | 4,796 | 5.55 | 856 | 213 | |
| Reserves | 7,060 | 5.53 | 1,257 | 6,182 | 5.62 | 1,117 | 140 | |
| Mineral Resources | Measured | – | – | – | 86 | 3.19 | 9 | (9) |
| Indicated | 1,050 | 3.62 | 122 | 614 | 3.35 | 66 | 56 | |
| M&I | 1,050 | 3.62 | 122 | 700 | 3.33 | 75 | 47 | |
| Inferred | 4,930 | 5.36 | 849 | 2,451 | 6.54 | 515 | 334 |
*The Mineral Reserves and Resources calculated for the Gokona underground mine at North Mara were as of 31st May 2019.
The Mineral Reserve and Resource upgrade follows the ongoing drilling programme which is taking place at the Gokona underground mine and has confirmed the predicted extensions of the orebody. In particular, an additional 95 drill holes totalling 32,463 metres have been incorporated into the updated Gokona Mineral Resource Model with the additional underground drilling information increasing the Gokona Mineral Reserves by 286Koz of gold; offset by mining depletion of 76Koz of gold and a conservative reduction in assumed crown pillar recovery of 71Koz of gold. New mining designs and a revised life of mine (LOM) plan have been created using this model which supports the update to the Mineral Reserve Statement.
The long-section indicating the changes to the mineral reserves and mineral resources as at 31 May 2019 compared to the 2018 year end are included below:
See www.acaciamining.com for pictures.
The Nyabirama Open Pit experienced some slope stability issues during Q1 2019 which led to a redesign of the open pit. The current work indicates that, aside from depletion, there will likely be a further 70Koz to 130Koz decrease in open pit Mineral Reserves. An updated open pit design is in the process of being produced and the statement will be updated as soon as the work is completed.
The gold price assumption used for Mineral Reserves for 2019 was maintained at US$1,200/oz. The Mineral Resource gold price used remained unchanged at US$1,400/oz. The updated Mineral Reserves and Mineral Resources calculated for Gokona were estimated as of 31 May 2019.
Acacia plans to continue underground diamond drilling at Gokona and this is expected to further increase confidence in the continuity of the mineralisation of the deposit with the potential for further additions to inventory in the Lower West and Lower East, as well as in the Deep East in the year-end 2019 Mineral Reserve and Resource. Accordingly, Acacia expects to provide a further update to its Mineral Reserves and Mineral Resources as soon as finalised.
