Coal resources on the Stockton Plateau are restricted to the Middle to Late Eocene aged Brunner Coal Measures (BCM). The BCM unconformably overlies the Ordovician aged Greenland Group greywackes and argillites, which has been extensively intruded by Cretaceous granites and porphyry (Berlins Quartz Porphyry). Due to the stratigraphic nature of coal measures, the coal seams generally lie in a horizontal or sub-horizontal plane. The resource has a dip to the northeast at the northern end of the deposit and to east along the western margin. Folding and faulting through the coal seams can create localised changes in dips up to 80°.

Stockton
The Mangatini coal seams are the main coal seams of the Stockton deposit. The seams have been given the abbreviation M. There are the three seams M1, M2, and the M3. The M2 seam is the predominant seam over the deposit and splits into four segregated seams in places. The M1 seam is thin and discontinuous stratigraphically below the M2 and not considered for resource estimation. The M3 is a rider seam to the M2 however the seam is discontinuous and often not recovered during mining. The M3 is not considered during resource estimation.

The Stockton resource area covers approximately 22.9km², a roughly rectangular shape up to 3.5km wide (E-W), and 8km long (N-S).

Within this area all seams are exposed in the operating mine, with in situ coal between 0m and 50m below the original ground surface.

Coa ........

Stockton
The mining method is conventional drill and blast, load and haul open pit mining operation. This utilises truck and excavator for waste movement, while coal is loaded using a combination of loaders and excavators with haulage to the run-of-mine (ROM) hopper CHPP, or stockpiles using dump trucks. The operations are supported by additional equipment including dozers, grader and watercarts. The selected mining method is based on long term experience of local conditions.

Minimum recoverable in situ thickness is 0.5m.

Specific parameters are applied to each pit. Pit designs have been based on geotechnical constraints and parameters. The typical highwall configuration is a batter height of 15m with batter angles between 30°- 76° using 8.5m wide benches. A maximum 10% gradient and 23m wide running surface is being used for in pit ramps and roads.

Pit limits have been updated based on pit optimisation studies with restrictions for current land and mineral access determined by mining permits and granted consent limits.

Additional recovery factors for Millerton, Hope Lyons and Rockies mining block areas include losses for historical underground extraction, fire effected coal, and where the overburden material has collapsed into the coal seam.

Approximately 61% of total Coal Reserve tonnes require washing to make a marketable product.

Minimum mining widths are dependent on volumes to be excavated and the siz ........

Contaminated coals from mining and/or from underground workings are processed via the company’s Coal Handling and Processing Plant (CHPP) since 2010. The CHPP removes the dilatant material and a small portion of coal to provide a more saleable product. The plants performance has been routinely monitored since its inception.

Stockton
Bypass Coal is defined as coal recovered that is not contaminated by rock or other materials and which when mined, is a saleable product (ash <8%).

Wash Coal is defined as coal that requires processing/washing prior to becoming a marketable product. The feed cut-off grade depends on the ash source, being either >8% and <35% if in situ ash, or >8% and <50% for coal contaminated with non-coal material.

Approximately 60% of total Reserve coal tonnes require washing to make a marketable product.

Stockton has a CHPP in operation to produce a marketable product.

The CHPP has an online analyser for ident ........