Ann: September Quarter 2014 Gold Production, page-21

Beardy,

MML state that the sustaining level of development ore is c. 30% of total ore for a running total of 100 working stopes.

However, that 30% of ore is blended with stope ore at the mill and is therefore expensed as part of the operating costs and appears as part of 'Cost of Sales' in the P&L statement.

Underground mines do have ongoing development costs in order to provide access to fresh stopes along existing levels and also at new, deeper levels, over time. But a substantial part of the development costs is capitalised (and annually amortised along with capital depreciation in the D&A component of Cost of Sales) because shafts, drives, ore passes, haulage tracks, etc, etc, remain an essential part of mine infrastructure throughout the mine life. Hence the carried amount of development expense remains a significant part of the Fixed Assets as shown in the balance sheet (currently US$261.7m) compared to US$115.4m for plant and equipments.

I do have some other comments and estimates that might be relevant to your post but will have to leave those for another time.
CPDLC