The local geological structure at Narrabri has been influenced by the presence of the Boggabri Ridge. The strata strike north-south and dip westwards at less than 5°. The stratigraphic sequence developed at the mine site includes the following units, described in descending order:

- Pilliga Sandstone – coarse grained quartz sandstone up to 60 m thick, which crops out in the western parts of ML1609 and EL6243;
- Purlawaugh Formation – up to 140 m thickness of thinly bedded sandstone and siltstone, with subordinate claystone and coal;
- Garrawilla Volcanics – up to 40 m thickness of alkali basalt flows with thin intervening mudstone and clastic rocks, unconformably overlying Triassic rocks where it is present;
- Deriah Formation – sporadically developed, lithic sandstone up to 15 m thick;
- Napperby Formation – siltstone, sandstone/siltstone laminate and fine- to mediumgrained quartz-lithic sandstone to 140 m thick;
- An intrusive basalt sill is present 30-35 m above the base of the Napperby Formation and is 15 to 20 m thick;
- Digby Formation – lithic, pebble conglomerate, typically 12-24 m thick, overlying the Black Jack Group; the boundary between the two being a low angle unconformity;
- Black Jack Group – consists of lithic sandstone, siltstone, claystone, coal and minor tuff; thickness is up to 70 m in the western part of ML1609 and less than 40 m thick in the east where the sequence is partially overlapped by the Digby Formation;
- The Hoskissons Coal, which forms the mineable resource at the property, has formation status and is part of the Black Jack Group;
- The Black Jack Group is underlain by a sequence of rock of marine sedimentary origin, namely the Watermark and Porcupine Formations;
- The marine sequence is underlain by the Maules Creek Formation, which is mined to southeast of Narrabri and is, in turn, underlain by the Leard Formation;
- The basement to the Gunnedah Basin sequence in the area comprises the dacite- to rhyolite- asalt and pyroclastic rocks of the Boggabri Volcanics.

The Hoskissons Coal consists of mainly of dull coal, comprising a lower ash basal section and a higher ash upper section. The full seam thickness within ML1609 and EL6243 is in the range 0 to 11.8 m thick; the seam is overlapped in the eastern part of the tenements by the conglomerate at the base of the Digby Formation. Over the area where the seam is being mined, and is planned to be mined, the full seam thickness is generally of the range 5-9 m thick. The basal 4.2 m section of the coal seam is defined as the working section for underground development within ML1609.

The Hoskissons seam is developed over an approximate area of 7,200 ha and occurs at depths ranging from 140 m in the east to 360 m in the west. The contained strike length of the coal seam is approximately 16 km whereas the down-dip width of the coal seam within the tenements is 4.5 km.

The Narrabri mine exploits coal from the Hoskissons seam. The seam is divided into two sections, namely an upper section (HC1) and a lower section (HC2). The lower section (HC2) contains low ash coal, suitable for underground mining and production of thermal coals (raw ash 8-13%). HC2 is 2.0 to 4.2 m in height and is the working section for the mine. The seam is thinnest in the east, where it is overlapped by the Digby Formation, but is consistently 4.2 m thick, allowing for thick seam longwall extraction. The upper section (HC1) contains high ash stony coal and tuffaceous claystone and as such, is higher in ash content.

The upper part of the seam (HC1) forms a mainly coal roof against the conglomerates of the Digby Formation, which is dominated by conglomerate (12-24 m thick) and consisting of hard lithic pebble- to cobble-size clasts (>100 mm) within a variable strength matrix.

Narrabri Mine has approval to use longwall mining methods to extract up to 11 Mtpa of ROM coal from the Hoskissons Seam within ML 1609.

The approved underground mining area encompasses a total of 20 longwall panels ranging in length between approximately 1.8 km and 4.0 km, depending on seam conditions and site constraints, and ranging between 295 m and 400 m wide.

The longwall design will be based on proven technology with an emphasis on reliability of equipment. The principal components of the system will include:
- Double-ended ranging drum shearer rated at 4,500 tph with full horizon control;
- An armoured face conveyor rated at 4,500 tph with provision for single tailgate drive and dual maingate drives;
- Beam Stage Loader rated at 5,000 tph; and
- High capacity two leg and four leg chocks shields with shearer initiation, base lift and high set functions.

Coal Processing and Transport
ROM coal is primary sized (nominally less than 200 mm) underground before it is transferred to the ROM coal stockpile on the surface via the drift conveyor. A reversible tripper stacks the ROM coal on the ROM coal stockpile in conjunction with dozers.

The ROM coal is then either fed via reclaim valves to a rotary breaker or by dozer push to a chain feeder which feeds a secondary bypass crusher. The rotary breaker reduces the size of the ROM coal to less than 125 mm before it is transferred to the CHPP. Waste generated from the rotary breaker is transferred to the REA.

The CHPP produces a combined (part washed) (thermal) and washed (PCI) coal products. Coal fines from the CHPP are blended with the unwashed (thermal) product coal. Coal (coarse) reject generated at the CHPP is disposed in the REA.

Product coal from the CHPP is transferred to the product coal stockpile via conveyor and dozers. The product coal from the se ........