I think also the yellow bars there, you can see we've been bringing the quality in as well as adding ounces. A portion of that deposit we've drilled to a grade control at about 12.5 meters spacing. I'm delighted to say the reconciliation has been beautiful, if not positive, in terms of tonnes, grade, and metal. Take a slice through that. I think the most obvious thing is the low stripping ratio. We are looking at kind of three deposits across there now. Those all zones individually around 100 meters each, which really translates into bulk mining, low edge effects. I think perhaps simple scheduling as well, particularly when we look at some of the metallurgy. It sticks out at surface, practically a zero strip when we start mining. I think the black shell was the 2 million ounce shell in February, and the blue shell was July's resource.
We've added ounces at depth. We've added ounces in the hanging wall. With that infill drilling, we really saw those zones bulk out and thicken up. The consistency in the deposit as we've lifted that categorization has been quite impressive. This year, I think we hit some, probably if I flick back to that slide, only a small portion of the deposit is kind of oxide transitional. This is a fresh rock deposit, which actually lends itself very well for heap leach in terms of percolation. When we did look at that oxide results, those kind of second numbers down there in our studies, we'd used 67% to about 73% for our recovery. It's first in time material going onto a heap leach pad. We were delighted with the 86% recovery. Metallurgically, we continue to make improvements and breakthroughs in the deposit.
All the gold is contained just as grains, 3 million gold in quartz only. This is one of the cleanest ores you'll ever see. No carbon, no copper, no arsenic, no sulfide. That is pervasive through the deposit, irrespective of geology. That's one of the biggest alteration overprints I've ever seen, which keeps the geochemistry very even. All that translates to a very simple processing and stacking schedule across the deposit. We did our PEA coming up to about two years ago now, and we're in the process of finishing our PFS, which is due in December. We're in September now. We were delighted with the 10 million tons for 10 years, producing about 122,000 ounces a year with a very elegant and simple stacking schedule. We doubled our stacking time in our production schedules from our test work. We discounted our recoveries.
Since that point, obviously, we've grown the deposit. What we are seeing in our studies at the moment with the PFS, and I think we're delighted with, is the fact that our operating cost structure is, I think we really got our numbers right in the PEA. The cost per ton to mine, $4.50, is probably a little bit conservative given that bulk mining approach. Our processing cost as well, we're very much in line with that study for, you know, in terms of a sort of view of the environment at the moment for what the PFS might look like. That really means a sort of an all-in sustaining cost of about $24 a ton. Our highest gold price we could even foresee was $3,500 Australian when we did this study. Obviously, we've blown past that a while away. That's our margin of about $21 a ton.
$21 a ton times 10 million tons per annum is a free cash flow of about $210 million. That really works towards some pretty exciting numbers in terms of project payback at that $3,500 Australian gold price. I didn't do the maths like Mark Bennett did on the U.S. gold price. We are starting to see a billion-dollar project, very attractive IRRs and rapid payback. Of course, the number on the right there, when I did this last week, we were looking at $5,400. Our study, I'll just reiterate, was done at $2,665. This is how we sit.
We do have a room full of a few Australians, but compared to some of our North American peers where heap leach and this kind of bulk mining is more appropriate, I think we have arrived on a global scale in terms of our grade, stripping ratio, recovery, and we've done our homework and our cost structure. I think it really puts us in quite a unique group of operators or operators to be. This is what the amount of detail, I suppose, that's gone into the pre-feasibility study. We have made a number of process improvements there. We have Caps Cassidy from Reno, Nevada, who are very heap leach focused running our study for us. You know, examples on there, particularly when we look at some of the exploration potential, you can see a gyratory crusher there, where in the PFS we had a jaw crusher.
I think that could give us some expansion capacity as we start to look forward. You see a couple of agglomeration drums. The refinements in the PFS are about making sure we deliver consistency of product to the pad. The pad is really a processing unit. I think as we've really refined our geological or geometallurgical model and aligned that with this study, confidence is really growing in that processing route. Exploration-wise, we've drilled 65,000 meters this year in both an infill and extensional component. I always like doing this. The numbers on the left, I think any kind of mill CIL operation would have been quite pleased with. Geographically, across the entire deposit, the numbers on the right really define an underlying architecture to this deposit, which I guess as a geologist, I've always known is there.
Our drilling's been a bit too wide spaced to be able to show everyone else, but some really nice high-grade, thick shoots are coming out of the deposit in a few zones. Another way of looking at it, if I do this, I'm going to use gold this time, draw a line down there. To the right of the line, we see a kind of bulk mining scenario. Orange blocks, red blocks, purple blocks, pink blocks, sorry. This side of it, we're seeing pink and purples only. It's really underlying, if you want, the bones of this deposit. We're going to have a look at it in a different way. If I zoom in on that, there have been some fantastic intersections repeat in these shoots. The black on this particular diagram is where those shoots are. I see Mark Bennett in the room.
I think I'm going to show you an intersection that you probably drilled several years ago on the next slide. I guess the point here is there's one there in, where are we, 1998, that might have been yours, Mark. Yeah, 21, 2020, 25, 23, we've been hitting these things. What you can actually see now at a 0.75 cutoff is how they all join together. As that infill drilling's gone in, the architecture has really come together. I'm going to look at that a different way and kind of simplify it. Iris, which is the one that's really grabbed the market's attention, this lode here, and the one we looked at on the long section. Why that's been so good is really simple. Two geological structures cross, and you see everything.
What you're looking at there on that slide is kind of classic conjugate set geology, where we see the repeat. Straight away, there's another exploration target for us. I'm going to do it now, turn the drilling on, and I'll turn that label off. You know, the classic geologist is going to go and he's going to drill along strike. That's quite obvious. We look at these structures here like this, straight through the middle of those two drill holes and drill sections. That's exactly what Iris looked like before we actually dropped the spacing down. We have a look at another opportunity here, and we extend long strike. There's another opportunity. There's another opportunity. I think there's another one straight through there where those high-grade intersections are.
If I zoom out, the one I'm really thrilled about, because we've had some beautiful intersections up here in the north, is this one, and this one, and this one. We think it's another one of them. The exploration potential here, I think, is just super size. I think it's been the biggest breakthrough the deposit's had with that infill drilling. Regionally, we maintain our exploration effort, and we will do this year. I think there's about 16 prospects on there now. I think it's worth highlighting since we've been here. We did pick up this ground down the south at Aquarius, really transferred over from Sumitomo Metal Mining. I think for them, I think they had a strong belief there was another kind of Karasu Dam geological system in there. I absolutely fully agree with them. That's an ex-Newmont colleague of mine who's Sumitomo's Chief Geologist now.
Maybe this wasn't big enough for a Sumitomo, but I think it could make a tremendous difference to us. That'll be an exploration target for the future. In terms of development schedule, you see there, PFS is due out in December. I think we're really heading for a positive study. I think we can improve on the PEA. That's the target. DFS commences immediately with October-November. Then into project financing and discussions. Permitting really begins at a federal, well, not a federal, but EPA level after we finish that PFS, and we're really trying to lock in the best plan possible now because of that EPA process, which can be about 18 months. That's it. Thank you very much. Any questions, you're welcome.
We'll time this up. One minute.
One minute.
One minute. Yep, if anyone has a question.
Yeah, you're making some very good points there about the advantages of bulk mining, driving those unit costs down. Not just mining, but that processing cost. You look at those North American peer group, those big heap leaches there. Are they achieving those sorts of unit costs? They're achieving a lot better. The difference, I suppose, here is we have to crush our rock. Like we're in the Archean in Australia. It's fresh basalt, dolerites. A lot of the North American operations there would be run of mine or much coarser crushers, and perhaps in mesothermal, Mesozoic kind of hydrothermally altered rocks. There is a difference in energy and wear and tear and capital. We have accounted for that in this.