@ozbucheron. Correct, I wrote erroneously "contained metal"...

@ozbucheron. Correct, I wrote erroneously "contained metal" whereas I meant grade. Waste can only add to contained metal.

However, as I explained above, the cut-off grade - resources relationship shows that the borders of the massive sulphide mineralisation are sharp with the waste having nil to very low metal grades. This means that a 25% increase in plant feed from waste with practically no grade should result in a drop in grade of close to 25%, not between 8% and 14%. Therefore there is an inconsistency.

For optimal use of longhole open stoping it requires that the outline of the deposit is regular and with sufficient inclination for free flow of broken rock, given the width of the stope. In addition, the wall rock must be competent enough not to scale and cause excessive dilution (the geotechnical work you refer to). Have a look at the reported intercepts. It shows often great variation over short distances. This points to the fact that open stoping can definitely not be used exclusively. Moreover, to employ a mining method that excessively dilutes high-grade ore is not very logical. The cost savings associated by longhole open stoping will be lost by having to deal with much more material to handle, haul and process. A method such as cut-and-fill is more costly, but will be much better at handling irregular contacts and limit dilution. A saving of 15% dilution amounts to approx. US$25 per tonne in revenue.