It is valuing future earnings, but it's not valued at much...

It is valuing future earnings, but it's not valued at much beyond future earnings from the salt slag portion of the aluminium division in Australia.

MHM have met their pre-upgrade revenue projections for the year since they started processing at Moolap, which is encouraging and that was with reduced capacity for extended periods. That adds creidbility to their post upgrade predictions IMO.
If they can show that they are on track to meet the post upgrade predictions of $8.6m p.a. then the $100m market cap isn't ridiculous, especially for a growth stock.

Most holders expect NMP processing soon, given that it has been installed at Moolap.
That will add significant revenue. We are also hoping for a buyout of the remaining 40% of the Australian rights, which would result in salt slag revenue of around $14m plus whatever the NMP returns, in which case it would be reasonable to expect the market cap to be higher than now, even without future plant builds and contracts.