Thank you for joining today's teleconference for the release of Mount Gibson Iron financial results for the year ended 30 June 2023. Mount Gibson Chief Executive Officer, Peter Kerr, will be leading the discussion and is joined by Chief Financial Officer, Gillian Dobson, and External Relations Manager, John Phaceas. Mr. Kerr will provide a brief overview, after which there will be an opportunity to ask questions. Due to time constraints, only institutional participants will be invited to ask questions at that time. A recording of the call will also be available via the Mount Gibson website shortly after completion of today's teleconference. Thank you, and go ahead please, Peter.
Thanks, Lisa. Good morning, all, and thanks for joining us to discuss Mount Gibson Iron's financial results for the 2023 financial year. As usual, I'll give a brief overview and then hand back to Lisa for any questions that may come from the floor. From an overall perspective, it was satisfying to see the significant underlying financial improvement we achieved over the course of the year. While sales in the first half were restricted following the fire incident in the crushing plant, once repairs were completed, Koolan Island commenced delivering the benefits of prior investments that we've made in overburden removal, ground support, and the crusher upgrade.
As noted in our last call in July, the June quarter was a record in terms of high-grade shipments and sales, delivering 17 shipments, which totaled 1.25 million wet metric tons in the quarter, double the rate of the prior quarter. We beat our revised full-year sales guidance of just over 3 million tons and more than trebled sales revenue to just over AUD 452 million free on board, FOB. Full-year cash flow, after all, capital expenditure and corporate costs totaled AUD 84 million, underpinned by reduced unit costs as sales lifted in the second half of the year, and the waste-to-ore stripping ratio continued to decline as we planned. I'll talk more about Koolan operations and unit costs in a bit more detail shortly.
On a group basis, this translated into a gross profit result of AUD 114.2 million, compared with a gross loss in the prior year of AUD 72.8 million. Following non-cash impairments of AUD 75.4 million and the de-recognition of deferred tax assets for accounting purposes of AUD 16.5 million, both of which are required under the accounting standards, as well as our usual other income and administrative costs, our net profit after tax was AUD 5.2 million. Although this is modest, given the gross profit level, it is a substantial turnaround from the AUD 174 million loss after tax recorded in the prior year.
The impairment resulted from our normal period-end obligations to review the carrying value of the assets in the context of prevailing conditions, including conservative iron ore price and foreign exchange outlooks, inflationary pressures, and higher prevailing interest rates. The key metric to keep in mind is our cash and investment reserves balance, however, which totaled AUD 162.4 million at 30 June 2023, and that was an increase of AUD 120 million over the second half of the financial year, which was also after repayment of the AUD 25 million that we drew down from our standby credit facility late last year. Turning to Koolan Island's financial performance, sale tonnage has doubled from the previous year to just over 3 million wet metric tons at a high average grade of 65.3% Fe.
Cash operating costs averaged AUD 77 per wet metric ton FOB that we sold, and that was before inventory build, project capital costs, and royalties. That was down from AUD 119 per wet metric ton in the prior year. That reflected the higher sales and the markedly reduced mine stripping ratio, which averaged 2.2 tonnes of waste for every tonne of ore for the full year and was down to 1.1 to 1 for the June half year period. Of course, the stripping ratio is a key driver of costs at Koolan Island. Consequently, the site generated operating cash flow of AUD 95.3 million in the year, on sales revenue of AUD 450.6 million, and a profit before interest and tax of AUD 44.1 million.
That compared with a loss of AUD 191 million and a cash outflow of AUD 188 million in the prior year. The key cash outflow items in the fiscal 2023 year just gone were cash operating costs of AUD 228 million, royalties of AUD 42.5 million, crusher repair and the interim processing arrangements that we've put in place following the fire of AUD 20.7 million, waste stripping investment of AUD 11 million, and sustaining and project capital costs totaling AUD 53.4 million. We expect unit cash costs to reduce further over the remaining mine life, based on a higher average level of sales and a lower average mine strip ratio of about 1.2 to 1 from here on, although this will vary at times according to normal ore and waste cycles within the main pit.
We talked about the mine's operational performance in detail at our quarterly call in July, so I won't say much more than that, other than to repeat that mining has been consistent over the last year, and we averaged about 1 million tons of high-grade iron ore extracted from the main pit each quarter. While our crushing capacity has enabled us to consistently ship between 5 and 6 cargoes per month during the northern dry season. We're targeting to achieve at least 4 shipments per month in the December to March wet season periods. Of course, that depends entirely on the kind of weather we face. That shipping profile is sufficient to support sales of around 4 million tons per year, which is the approximate run rate we expect to maintain going forward.
Finally, as reported after period end, we recently incurred a localized rockfall in a section on the eastern footwall, on the island side, that is, of the pit. The event was detected in advance by the site's continuous radar monitoring systems, and no injuries or equipment damage occurred. The area impacted is not currently being mined, and all production is not scheduled to occur in that particular location until the March quarter next year. In good news, based on the initial geotechnical evaluation, it's currently expected that remedial measures can be implemented to enable mining to recommence in that impacted zone with minimal impact on the current mine plan.
A detailed geotechnical assessment is now underway to further define those measures, which are likely to include the use of additional strengthened avalanche mesh material, as well as cable bolting and shotcreting, typical for ground support activities at the Koolan Island operation. In relation to the Mid-West business, while our focus has obviously been on the turnaround of Koolan Island, the Mid-West business still generated a positive AUD 6.5 million pre-tax profit for the group. Our ongoing rail credit refund brought in just over AUD 9 million in the year. The proceeds to date since that started are AUD 33.5 million, out of a total capped entitlement of 35. Obviously we expect to receive the final proceeds of that entitlement this current financial year. The business also generated modest income from third-party use of our available storage capacity at Geraldton Port.
The more significant development, however, was our transaction announced in late June to divest the company's Mid-West iron ore mining interests at Shine and Extension Hill, and the Geraldton storage shared assets to fellow regional iron ore producer, Fenix Resources. We did that for AUD 10 million in cash, 60 million shares currently worth around AUD 18 million, and 25 million 5-year options in Fenix. These are exercisable in 2 tranches of 12.5 million options each at AUD 0.25 and AUD 0.30, respectively. Mount Gibson is now Fenix's largest shareholder, with an interest of approximately 8.6%, and with the option, there's scope to increase this. As part of the transaction, Fenix has also assumed the remaining rehabilitation obligations across the various asset sites, which we had provisioned at 30 June 2023 at approximately AUD 8.2 million.
As recently announced, this transaction was successfully completed on the 21st of July. For Mount Gibson, the deal crystallized value for assets that's not yet reflected in share price, as well as giving ongoing exposure to Fenix's growth-focused, iron ore mining and integrated logistics business in the Mid-West. We consider the transaction as a win for both companies, as well as for the Geraldton Port and Mid-West community, in which we've operated for many years. The sale now also frees us up to focus on maximizing cash flow from Koolan and the pursuit of new investment opportunities in other commodities, notably base metals, to provide longer-term operating cash flows.
In relation to our exploration activities, we've also recently, and this is after a number of years, recommenced our regional exploration efforts in the Mid-West, focusing initially on prospective base metals targets near our Tallering Peak site and to the north of the Butchers Track project in the Murchison. Further farming and joint venture opportunities are also being reviewed. I'd just now like to touch on market conditions and outlook. Iron ore prices were slightly lower in the 2023 financial year, albeit still at attractive levels, and this was driven by the weaker than anticipated rate of post-COVID recovery in China and global economic uncertainty, which translated into general inflation and higher interest rates across the globe. I'm sure everyone's familiar with monitoring the Chinese economy, in particular, its construction, demand, and property sector, which are key drivers for iron ore exports from Australia.
The benchmark Platts 62% index averaged $110 per dry metric ton CFR, so that's the price delivered in northern China for the year, and that was a decline of around 20% from the previous financial year. While importantly for us, the 65% Fe index price, and that is the price at which the Koolan high-grade fines contracts are pegged, averaged $124 per dry metric ton CFR for the year. The 65% Fe index average premium above the 62% index remained reasonably steady at about 7% per contained metal unit, and this is a premium that is captured under our high-grade sales agreements and is important for us.
Despite the lower market prices, Mount Gibson's average realized price increased almost 30% to $103 per dry metric ton FOB, so that's the price out of Koolan Island, compared with the prior year. That was reflective of the fact that a significantly increased volume of high-grade 65% Fe fines accounted for all of our sales in this last financial year. We also enjoyed another boost from the weaker Australian dollar, which averaged just over $0.67 for the year, compared with $0.72 in the prior year. We continue to see good demand from our customers for the high-grade and low-impurity iron ore products from Koolan Island, and we're anticipating a strong year ahead.
In relation to production and cost guidance for this 2023-2024 financial year, we're targeting high-grade iron ore sales from Koolan Island of between 3.8 million and 4.2 million wet metric tons at an average unit cash cost of AUD 65-70 per ton FOB sold, and that's before royalties. In relation to dividends, you will have seen in the earnings announcement that a final dividend has not been declared for the 2023 financial year, given the continuing focus on increasing shipments and profitability from Koolan Island. However, the board has clearly stated its intention to resume paying dividends going forward and will review dividend capacity, including the expected generation of franking credits at future interim and full year periods.
Just remind people that Mount Gibson has historically, over the last 11 or 12 years, paid about AUD 330 million fully franked dividends. Before I wrap up, one final matter, I just want to express my thanks to Russell Barwick for his valued input and contribution to the company as a non-executive director over the last almost 12 years. He has stepped off the board today due to his increased personal business commitments. In addition, I welcome Ms. Evian Delfabbro to the company when she takes up the role of independent non-executive director next week. Evian brings key business, commercial, and legal experience with her, including in mining construction, and we look forward to working with her going forward. With that, I'll finish up and hand back to you, Lisa, for any questions you may have.
Thank you, Peter. If anybody would like to ask a question, please press star one on your phone now. It's just star one on your phone if you have a question. Thanks, Peter. We don't have any questions.
Okay. Thanks, Lisa. Thank you all for listening. If you do have questions or you want to ask us something offline, then please feel free to phone either John Phaceas or myself on the numbers listed. Please have a good day. Thank you.
Thank you, Peter. The conference is now in moderator only mode.