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 ........

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 ........

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