Total Koolan Island Mineral Resources and Ore Reserves comprising the Main, Acacia East and Mangrove Deposits.

Koolan Island, Main Deposit
The mineralised zone is an overturned enriched haematitic sandstone horizon within the Yampi Sandstone Member unconformably overlying the Elgee Siltstone. It is between 12 and 30 metres thick, and dips 55 to 80 to the south.

The Main deposit mineralisation is approximately 2,000 m in length and is currently modelled to approximately 215 m in depth below mean sea level. Mineralisation continues and extends beyond this depth however further infill drilling is required to define this area with confidence. The resource is open at depth.

Koolan Island, Acacia East Deposit
The mineralised zone is an enriched haematitic sandstone horizon within the Yampi Sandstone member unconformably overlying the Elgee Siltstone. It is between 8 and 20 metres thick, and dips 45 to 60 to the south.

The Acacia East mineralisation is approximately 1,500m in length and is modelled to approximately 300 m in depth.

Koolan Island, Mangrove Deposit
The mineralised zone is an enriched haematitic sandstone horizon within the Yampi Sandstone Member unconformably overlying the Elgee Siltstone. It is between 12 and 30 metres thick. The mineralised unit is overturned and dips from 80 to the south in the west, twisting to right way up and 80 to the North in the east.

The Mangrove mineralisation ........

Koolan Island, Main DepositThe deposit has been mined by conventional open pit mining methods, utilising industry standard practices of drilling, blasting, and load and haul using hydraulic backhoe excavators. The overburden waste has been removed by large size excavators with bulk mining method. Where required medium size excavators have been used for selective mining of ore. Known mining parameters from Main pit were used in the optimisation and pit design.

Modelling of mining dilution in three dimensions is by the digital application of a dilution skin around the ore in the Mineral Resource model. Metallurgical parameters are then added to the diluted model. The final diluted mining block model is used directly for pit optimisation and scheduling, without the further application of global factors.

Mine infrastructure is well established following 9 years of mining operations. The physical width and therefore depth of Main Pit is constrained by the final hanging wall pit limit relative to the position of the seawall.

To ensure safe access for future mining in the western end of the Main Pit, Mount Gibson has engaged a specialist contractor to undertake geotechnical footwall ground support bolting.

During 2021/22, Mount Gibson achieved total ore sales, with the operational focus on completing the Koolan Island waste stripping program, upper footwall ground support program.

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