Thank you for joining today's teleconference for the release of Mount Gibson Iron's September quarter 2022 activities report. Mount Gibson Chief Executive Officer, Peter Kerr, will be leading the discussion, and he's joined by Chief Financial Officer, Gill Dobson, External Relations Manager, John Phaceas. Mr. Kerr will provide a brief overview, after which there'll be an opportunity to ask questions. Due to the time constraint, only institutional participants will be invited to ask questions at that time. A recording of the call will be available via the Mount Gibson website shortly after the completion of today's teleconference. I will now hand you over to Peter Kerr. Thanks, Peter.
Thanks, Lisa, and good morning all, and thanks for joining us to discuss Mount Gibson's September quarter activities report. As usual, I'll give a brief overview before handing back to Lisa for any questions. The September quarter, as people know, was obviously dominated by the impact of the mid-August fire within the product screening area of the processing plant at Koolan Island. Our focus since then has been on recovering from that incident as quickly as possible and getting back to increasing shipment numbers as soon as we're over. The fire was obviously very disappointing as it interrupted what had been a very strong improvement trend at Koolan as we started to realize the operational benefits of last year's investment in both overburden stripping and the ground support programs, as well as various other capital improvement projects at the site.
After a strong start to the quarter, in which we completed four high-grade shipments before the plant fire on the 12th of August, processing and shipping from then on was restricted, and that had a corresponding temporary adverse impact on our revenues and cash flows in the quarter. Repairs to the fire-damaged product screen section of the plant are going well, while our interim processing strategy of utilizing mobile crushing capacity is now also being optimized and improving. The net effect is that we expect to be back to full capacity in January, while the strong performance of the mining team in building up stocks of high-grade iron ore for processing as the main plant comes fully back online, does position the operation strongly to significantly increase sales in the June 2023 half year period.
Consequently, we maintain our current sales guidance, 3.2 million-3.7 million wet metric tons of high-grade ore in this financial year, fiscal 2023. Obviously weighted to the second half at an average cash operating cost before royalties, for the full year of AUD 70-AUD 75 per wet metric ton FOB that we sell. Looking at the activities at Koolan in more detail, total ore sales were 451,000 tons of 65% FE material in six shipments, two of which were completed after the plant fire in August. From a mining perspective, performance was good.
Total material movement lifted to 4.6 million tons of waste and ore, and importantly, the stripping ratio reduced further in line with the plan, averaging 4 tons of waste for every 1 ton of ore in the period, on track to average 3.5/ 1 across this current half year, and then 1/ 1 in the June 2023 half-year period. From today forward, the average stripping ratio for the approx 4.5 year life of the mine in the main pit is only 1.3/1 . Assisting the mining productivity, the replacement of the primary mining fleet is going well, with the last two of eight new haul trucks being delivered to site this week.
These trucks are well suited for the main pit and will continue the progressive demobilization of the old pre-2014 haul truck fleet in coming weeks. Similarly, we are replacing the aged primary production excavators with the first of two new units to be operational in the main pit within the next week. Importantly, now that the peak waste stripping phase is effectively complete and the upper footwall ground support works are now finished, high-grade iron ore production rose to 915,000 tons in the quarter, extracted from the main pit. That was 38% higher than the June quarter as access to the ore body further opened up across the floor of the pit.
With processing temporarily restricted, we made the decision to continue mining in accordance with the production plan and to build substantial high-grade ore stocks for processing once the main pit comes fully back online. Run of mine ore stocks in front of the plant currently total well over 500,000 tons. This will enable a rapid processing catch up as crushing capacity returns. It'll also provide us with some added flexibility to mitigate any disruptions during the coming Kimberley region wet season. In relation to processing during the quarter, just over 600,000 tons was crushed. Two-thirds of this was obviously before the fire incident. In terms of fire recovery progress, our key focus is obviously on the recovery activities as quickly as possible.
As we reported previously, the fire occurred in the product sizing screen area of the plant, and that was during a maintenance shutdown. All personnel in the area were evacuated and there were no injuries other than some smoke inhalation treatment. The fire damaged, unfortunately, the product screen equipment, the associated feeder and conveyor equipment, as well as some of the surrounding steel structures. The processing recommenced in early September, and that's utilizing the undamaged front end components of the main plant. Mobile crushing equipment was mobilized during the month to process oversized material that requires further crushing and screening to meet shipping specifications. Crushing capacity utilizing these interim arrangements has steadily increased and is presently running at approximately 70%, some days more than that, of normal capacity while repairs to the plant are undertaken.
Repairs are actually progressing ahead of initial expectations. We expect them to be completed in January. Replacement screening equipment, structural steel, and other components, even within this difficult supply market, have been procured quickly and fabrication works are well underway. Accordingly, we anticipate returning to full processing capacity early in the March quarter, with shipping rates increasing from that point to 4 to 5 shipments per month going forward at a minimum. Also note that Mount Gibson maintains relevant insurance cover for incidents such as this. Discussions are progressing with our insurers as we prepare to submit an initial claim.
On the cost front at Koolan Island, unit mining, logistics, and administration cash costs, which include all transport and logistics charges for the island-based operation, were AUD 12.26 per ton of ore and waste moved in the quarter. That was slightly improved on the rate of AUD 12.49 per ton in the prior quarter. That reflected some good work from the site's mining teams and ongoing productivity and cost focus. Unit cash operating costs equated to AUD 67 per ton, the wet metric ton sold FOB, so that's at Koolan Island, in the quarter before inventory build, royalties, and some residual capital projects. That figure compares with AUD 77 per ton FOB sold in the June quarter. Unit costs are expected to be temporarily higher in the December quarter while the plant repairs are undertaken and shipping remains restricted.
Then they will progressively reduce over the March and June quarters thereafter, consistent with the company's financial 2023 year cash cost guidance of AUD 70-AUD 75 per ton before royalties. Sales revenue in the quarter totaled AUD 62 million FOB, reflecting a realized price of $96 per ton sold FOB. That's after shipping freight. This reflected the average Platts index price for 65% FE material of $115 CFR in the quarter, and the average shipping rate charge of approximately $17 a ton. Shipping freight rates have continued to decline in recent weeks and are currently around the $15-$16 per ton level.
The Koolan Island operation incurred a net cash outflow for the quarter of AUD 22 million, reflecting the decision to continue to mine in accordance with the existing mine plan and build the substantial high-grade stocks while the processing plant repairs are undertaken. These stockpiles, sitting ahead of the processing plant, have a current market value in excess of AUD 60 million once they're processed. You can see why we've continued to move ahead with mining. Revenue for the quarter totaled AUD 62 million, obviously as I've discussed, key site outflow items were cash operating and sustaining capital costs of AUD 30 million, the build of high-grade iron ore inventories, which has cost us AUD 46 million, royalties of AUD 6 million, and residual capital projects of AUD 2 million, which related primarily to completion of the upper footwall ground support project in July.
In relation to the group, the net cash outflow for the quarter was AUD 26 million, comprising the Koolan Island numbers I just mentioned. Net inflows from Midwest assets of AUD 1 million, including the ongoing rail credit, interest and other income of AUD 1 million, exploration costs of AUD 1 million, and then corporate costs and realized foreign exchange and financial asset movements together totaling AUD 5 million. After working capital movements of AUD 39 million, relating primarily to the substantial downward provisional pricing adjustments, most of which was provided for in the fiscal year 2022 results, the company's cash and investment balance was AUD 60 million at the end of the quarter. In terms of outlook, as mining to build the high-grade stocks will continue while repairs are completed in the plant.
Our operating cash flow at Koolan Island is anticipated to continue to be negative in the December quarter before turning positive and substantially increasing as the plant comes fully back online in the March quarter and our shipment volumes rise. Accordingly, in the current quarter, we will also temporarily draw on the company's existing AUD 100 million revolving corporate debt facility for a short period, and that enables us to continue mining as productively as possible. We expect strong cash flow generation in the June 2023 half year as the substantial high-grade ore stockpiles are then processed and shipped. In summary, we're bridging through the temporary disruptions associated with the Koolan Island plant fire repairs, and good work is being done by the team on site. We continue to export high-grade ore and build substantial ore stocks for shipping for when the plant comes back online fully.
The fiscal 2023 financial year will be a strong one for the company operationally and financially, notwithstanding this temporary setback, as benefits of significant mining investments, in particular, the waste cutback, that was made in recent periods, begin to deliver. We therefore look forward to maintaining a rising production and cash flow trajectory and replenishing and growing the company's cash reserves as Koolan Island consolidates its position as Australia's highest-grade direct ship ore hematite producer. With that, Lisa, I'll hand back to you for any questions that any listeners may have.