The Middlemount resource contains the coal seams of the Rangal Coal Measures and Burngrove Formation of the Blackwater Group. The target seams within the resource consist of the Roper, Middlemount, Tralee and Pisces Upper seams (in descending order) which belong to the Rangal Coal Measures, while the Pisces Lower and Girrah seams belong to the Burngrove Formation and are not considered to have economic potential based on current studies.

Overlying the Rangal Coal Measures are alluvial sediments, inferred to be Tertiary in age, with a thickness of up to 30m. The depth of weathering averages 45m, ranging from 20m in the southeast to over 60m in the central and northern areas of ML70379.

The Middlemount and Pisces seams have been subjected to the majority of the exploration mining works. The Middlemount seam averages 4.0m thick in the area west of the Jellinbah Fault, ranging from less than 2 to over 7 m. The Middlemount Upper working section is a high ash section that is present over most of the Middlemount area – the exception is in the north, where it is less than 0.3m thick. The top section of the Middlemount Lower Section is predominantly dull with some bright banded coal with an average raw coal CSN average of 1 to 1.5. The base section of the Middlemount seam has more bright coal than the top section and the average raw coal CSN is 4 to 5.

The Tralee seam underlies the Middlemount seam. At Middlemount, it ranges in thickness from 0.5 to 1.0m when it occurs just below the Middlemount seam (within 10m). The Tralee seam is divided into three working sections (TL1, TL2T and TL2B, top down) and similar to the Middlemount Lower seam the working section division is predominantly based on coal brightness. Where the seam splits further from the Middlemount seam, the Tralee seam thins to usually less than 0.3m.

The Pisces Upper seam averages 4.8m thick in the area west of the Jellinbah fault, ranging from 2 to over 6 m. Thickening and thinning of the seams is interpreted to be the result due to the same structural effects as noted for the Middlemount seam, while intersections outside this range were similarly excluded from the coal thickness model. The Pisces Upper seam is divided into three working sections (PUT, PUM and PUB, top down) and similar to the Middlemount Lower seam the working section division is predominantly based on coal brightness.

The Middlemount Seam is stratigraphically equivalent to the Leichhardt seam or Elphinstone seam of the Northern Bowen Basin, or the Pollux Seam of the Central and Southern Bowen Basin and the DU and D seam of the south-eastern Bowen Basin at Moura. The Pisces Seam is the stratigraphically equivalent to the Vermont or Hynds Seam of the Northern Bowen Basin and the E seam of the south-eastern Bowen Basin at Moura. The RPM Competent Person is familiar with the characteristics of the Middlemount and Pisces seams throughout the Bowen Basin.

The potential open cut coal area strikes north-northwest and dips to the east at between 3- and 7-degrees; the deposit is approximately 7km long and 2km wide. The resource is limited to the east by the Jellinbah Fault; a major regional thrust fault which is oriented north- northwest and has displacement greater than 300m. This fault is located close to the boundary of ML70379 and ML 70417. The coal seams of the Rangal Coal Measures crop out to the west of the Jellinbah Fault, where the majority of the coal exploration has been completed. The strata present on the eastern or upthrown side of the Jellinbah Fault are from the Burngrove Formation, which are becoming visible in the highwall of the mining excavation.

Exploration drilling and mining has identified that the deposit is complicated by localised thickening of seams in the vicinity of faults. Other than the Jellinbah fault, the deposit contains small-scale (<10m) normal and thrust faults, which is evidenced by the thickened and thinned Middlemount and Pisces seam intersections and by the changes in structural elevations between boreholes.

Middlemount uses conventional truck and excavator methods. Coal mining activities is carried out on a 24 hour a day, 7 days a week basis.

Mine Design
The following outlines the mine design aspects of Middlemount operations.
- The geotechnical design criteria that are applied at Middlemount can be summarised as follows:
- A 35° degree slope for the low wall in weathered Permian and Tertiary/Cenozoic sands;
- Individual 50° degree batter slopes for highwalls, sidewalls and endwalls in weathered Permian and tertiary/Cenozoic sands. 10m berms are included every 12m vertically to give an overall slope angle of approximately 35°;
- 25m berm for the highwalls and on top of the fresh Permian. On some endwalls a 50m haul bench is included;
- Individual 70° slope for the highwalls, sidewalls and endwalls in fresh Permian;
- Above the cast blasting zone 25m berms are included approximately 50m vertically to give an overall angle of 55°; and
- A 25m berm is included on top of the cast blasting horizon.

Middlemount operations are contained within two Mining Leases (ML’s) and one Mineral Development Licence (MDL). The area covered by these licenses and permits is about 1,600 ha with the area having approximate dimensions of 5 km north south and 2 km east west.

Pit Limits
The open cut pit limits at Middlemount are based on the following criteria:
- An off set of 50m on the Middlemount seam from the Jellinbah fault on the eastern side of the deposit;
- An off set of approximately 300m on the Pisces Upper seam along the northern boundary of ML 70379;
- The southern boundary within ML 70379 is the diversion and flood protection levee associated with Roper Creek.

The Middlemount CHPP designed in 2007 and construction was completed in 2010. The plant has had modifications completed to aspects of the design in 2011 which were aimed at improving coking coal yields from the plant. The CHPP is a single stage plant with the ability to produce two products. The plant uses standard industry technologies which includes; dense medium cyclones, spirals and Jameson cell systems.

The Middlemount plant has a nominal throughput capacity of 700tph and operates 24 hours per day, 7 days a week. This is sufficient to process up to 5.4Mtpa of ROM coal feed. The Middlemount plant operates at high utilisations by industry standards.

All ROM coal at Middlemount is washed to produce two product types: a semi-hard coking product at 10.5% ash with CSN of 6 and CSR of 58 to 63 and a low-volatile PCI coal at 10.0% ash. The CHPP is a 700tph single stage plant with two product coal handling systems and uses industry standard technology, operating at high availability.