Perhaps not relevant here but - Royalty systems In Western...

Perhaps not relevant here but -

Royalty systems

In Western Australia, there are two systems used to collect mineral royalties:

• Specific rate – calculated as a flat rate per tonne produced – generally apply under legislation  to construction and industrial minerals.
• Ad valorem – calculated as a proportion of the ‘royalty value’ of the mineral.  The royalty value is broadly calculated as the quantity of the mineral in the form in which it is first sold, multiplied by the price in that form, minus any allowable deductions.  In some cases an alternative to ‘royalty value’ applies e.g. nickel.

Ad valorem

The ad valorem or value-based rate of royalty, which applies under the Mining Regulations 1981, is based on the following principles:

• bulk material (subject to limited treatment) – 7.5 per cent of the royalty value
• concentrate material (subject to substantial enrichment through a concentration plant) – 5.0 per cent of the royalty value
• metal – 2.5 per cent of the royalty value

Does any of this have to do with Mine Head Valuations?

I'm none the wiser