AISC, page-2

Unfortunately the actual AISC won't be known until gold ore comes out of the ground, is processed and gold poured.
AISC for Gold producers can vary widely, as you no doubt know, dependent on the cost structure of the operation. For example a plausible range for SNG might be $600oz - $2200oz fundamentally driven by the spatial grade variability of mineralised zones and the existence of relatively high grade gold ore shoots.

Factors affecting AISC include, mining and processing costs, administration, royalties, sustaining capital and any other expense. You can take comfort that BR is not known for wasting money.
A decision to mine will be subject to achievable head grades of the gold ore (controlled at time of extraction), prevailing A$ Au price (spot or hedge) and AISC. Clearly no one can control the A$ Au price, however high grade narrow vein mining production has a high percentage of variable costs and lends itself to production volumes being dialed up or down depending on Gold Price fluctuations and cycles.

Your best insight to the viability of SNG, at this time, is in the Gold Grades - the ones already known about from the SNG prospectus.
RED, from their underground operations, have just reported (see data below) for the Dec-Qtr production of 21,534oz, AISC A$2,181/oz at a head grade of 2.73g/t.
Compare this to the historic mining records for the SNG tenements. As the extracts from the SNG prospectus show, very significant volumes of high grade ore (anything < 15g/t) were left behind. Why.....because lower grades required physically moving increasing amounts of ore for the same quantity of gold.

If SNG applied a 5g/t cutoff grade to early stage mining operations, the same quantity of gold can be won by mining and processing half the tonnage of ore compared to a low grade underground operation such as RED.
The result being a significant reduction in AISC, that is $/oz of Au produced.

Base operating case would be near term mining of the known (historical mining records + existing drill data) shallow ore shoots. Mining techniques and costs for narrow vein mining of this style of gold mineralisation are well known to management (BR - Eltin Mining and ACM).
A bulk sampling program in remnant areas will quickly confirm expected head grades and mining/processing costs. Contractors can be engaged to provide labour and items of capital equipment. Administration costs are already effectively covered by the current exploration program and minimal sustaining capital would be required if ore is trucked to an existing mill. A one of cost would be re-establishing access to the remnant working or access to new outcropping ore shoots.

If it makes sense to generate early cashflow by mining remnant areas and known ore shoots open at depth, I would like to think BR will action that strategy.


Top 200m vertical cross section of Big River Mine (Source: p. 131 SNG Prospectus)

Red 5 Limited - Data
I am watching RED5 Limited, currently in production. I am not familiar with the Darlot mine, however it is one source of data if you are wanting to construct an AISC model. SNG near term production would not carry the capital or administrative costs being born by RED (See RED forecast AISC table below).
@Goldhunter122 may be able to direct you to another operation that is in production and more representative of future mining of the Reefton Complex.

Here is an extract from RED Half-Year Financial Results for 6 Months to 31 December 2020 released to the market on 25 Feb 2021. Note the head grade of 2.73 g/t Au.

Darlot contributes 26,616oz, AISC not disclosed. Production at Darlot was underground predominantly associated with mining in remnant areas.
Combined Darlot and KOTH results are:
Sep-Qtr production 20,283oz, AISC $2,126 and Dec-Qtr production was 21,534oz, AISC A$2,181/oz. (Source: RED quarterly result announcements).

For comparison with Reefton (SNG), I include the following Darlot Resource data (RED).




RED are forecasting AISC as setout below:


You may have already seen this investor overview for the Blackwater Mine, in case you have not, here are some interesting numbers from Federation Mining. (Source: Federation Mining - Website https://www.federationmining.com.au/wp-content/uploads/2020/04/Federation-Mining-Five-Year-Strategy-Website.pdf )


Good luck constructing a model if you wish to forecast AISC for SNG.