I imagine this is mostly due to the fact it's cash receipts not...

I imagine this is mostly due to the fact it's cash receipts not revenue. Production amounts are a leading indicator for the following quarter's cash receipts/revenue, when concentrate is sold and cash is then later collected. Revenue is recognized once a customer takes possession of the concentrate at the gate (I believe that's the case, a quick check of last years annual will confirm), cash receipts will then lag from possession of concentrate for between 30-90 days depending on terms (guessing here). Cash is king so these quarterly reports are important to understand liquidity of the company but the half yearly and annual reports are what will more accurately show us the production cost vs revenue directly earned as a result.

You probably want to reference receipts for equivalent seasons to build a baseline. Using financial year quarters aligning with wet season (not calendar as you're doing above, might be some confusiong between yours and management numbers there): Q2/3 2021 receipts totaled ( Q2/3 2022 receipts totaled $2.031m (1.209m + 0.822m) and Q2/3 2023 of $3.053m (2.281m + 0.772m). From what I recall the Q2 2021 I think had a big chunk of that large quarry cash receipts included so perhaps that's why. I should really compile some of this information so I can reference it more easily, apologies if I've mixed any of these amounts up as I just did a quick scan of past cashflows.