Terrestrial Mining Stories
Terrestrial Project Concept Development Stories
I have seen, ‘up close and personal’, the economic and concept definition stories in multiple mining projects: Mary Kathleen, Jabiluka, Olympic Dam, Nolans Bore, Mulga Rock, Jacinth-Ambrosia, Mt Keith Nickel, the Kambalda-Kalgoorlie-Kwinana nickel industry, the Browns Range HREE project, and have ‘industry cultural heritage’ exposure to others: the Darling Scarp bauxite deposits, Mt Isa Mines, the Sydney Basin Coal Measures (where I grew up), the Bulolo Gold Dredging story in PNG, and others.
Mary Kathleen Uranium:
First operation (1958-63, produced 4,000 tons of yellowcake) basically launched Rio Tinto as a credible organization. It was at that stage one of the biggest U mines in the world..
Long and very painful rebirth for second operation (1976-82, 4,300 t U3O8). Why painful? Because the grade was a lot less: because of worse waste-to-ore ratio, they went to bigger equipment and therefore less selective mining method, and the drop in grade was worse than expected. And the upgrade via radiometric sorters only ‘sorta’ worked. Result: they had headgrade to mill of 0.08% when they had expected headgrade to mill more like 0.12%. (Ouch..) To make budget, they had to squeeze >50% more tonnes thru the mill, which was not up to it, and thus kept failing…
Learnings: Grade is crucial. So is adequately conservative mine and project planning.
Jabiluka:
Briefly touted as the world’s biggest uranium deposit (never went ahead, due to govt and then Traditional Owner resistance). Engineering demands (water balance in the wet tropics) prompted the transition from open pit design to (totally different–) underground design. This gave massive reduction in rainfall footprint, massive reduction in waste rock dumps footprint, hence massive reduction in environmental cost and risk, and gave big, big reduction in capex and opex (positives), but inserted into the equation other risks (rockfalls underground, and radon in underground U mines), which was where I came in.
Learnings: Sometimes the environmental /risks review throws up a showstopper; in which case, you have to go back to the project concept to see if there is another way to do it.
Olympic Dam:
Olympic Dam in central South Australia is a massive copper-uranium-gold-silver orebody in a haematitic breccia also loaded up with rare earths. ‘It is the biggest uranium deposit in the world, and one of the ten biggest copper deposits.’
When it was discovered in the mid 1970s (the orebody is at 400 metres depth) one of the first questions the proponents wondered about was whether it was amenable to open pit mining versus underground. Back-of-the-envelope estimates showed however that it would cost $2 billion in ‘dollars of the day’ to ‘skylight’ the ore, thus making open pit impractical economically.
This presented a political and technical challenge, as the perception had arisen that all underground mining of uranium ores was in principle unmanageably dangerous. (Reasonable, given that lung cancer rates in the 1950-1960s Utah-Colorado U miners had been 20 x normal.)
This perception had to be checked against reality in the case of modern, well-engineered and (critically) well-ventilated underground operations; and, then rigorously, pedantically, and technically, put to bed. In the process, we had to choose specific underground mining methods which would allow for adequate ventilation and adequately safe air quality re radon decay progeny concentrations. Some mining methods would have delivered poor and indeed over time, ‘showstopper’ conditions. (all of that was my specific job…)
As to the means of extracting the value, we did not know at first (and it only slowly became obvious) what process flowsheet we would use. The front end would be crush, grind, float to produce a copper sulphide concentrate; that was pretty obvious. The flotation ‘rejects’ carried the bulk of the U which would go to a normal acid leach, solvent extraction, ammonia precipitation, calciner process to make ‘yellowcake’. But then, what to do with the copper concentrate? The choices were roast -atmospheric leach – electrowin, or pressure leach – electrowin, or smelter then electrolytic refinery. The choice was to go the smelter route. All these processes were predicated on producing final processed ‘four nines’ (99.99% pure) cathode copper product on site, so as to categorically avoid any concern with shipping ‘radioactive’ copper concentrate.
So, proposal was for what would be the biggest underground mine in the country, mining (eek!) uranium, and a huge treatment plant complex to produce yellowcake, cathode copper, gold, and silver (that used to take me two hours to walk end to end).
(desert looking a bit greener than normal in this piccie..)
The go-ahead was thus a very ballsy decision, even tho’ much of the technical risk was retired by pre-commercial underground expln development (20 km of drives, over 5 years, ca $50M!) and by a $20M,100-man, 2-yr-campaign, large-scale pilot plant..
Learnings: a Trial Mine and Demo / Pilot Plant can be very useful to retire technical risk.
The pre-production trial mine was developed via a fullscale shaft-sink, with fullscale underground development. The decision to go to shaftsink was taken at a time when the WMC Board still knew very little about the mineralization (except that it was very big). The BP Joint Venturers were tightwad and argumentative and firmly against the decision to go fullscale in u/g development. I was in the room watching the argument develop. The old BP/Seltrust mining guru was arguing (for cost reasons) for small-scale tunnels to get out to the laterally distributed target areas where we were to do underground expln drilling. The young, WMC project mining engineer, Bob Crew, pushed back with the argument ‘you need full-size equipment to get rapid development, you want to get out to the target areas fast, use proper mining gear; and then when the go-ahead for fullscale mining is given we don’t have to go back and waste time stripping out to get bigger size tunnels.’ He won.
Another learning: there are circumstances where it makes sense to go straight to production-scale equipment so you can seamlessly transition into production when ‘the time comes’..
(note: this also applies in the oil industry: wildcat wells are drilled using fullscale equipment, so that if they do produce payable flows then they can be hooked straight into the downstream collection system..)
Another ‘learning’: Sometimes, even going into the Final Feasibility Stages, you still haven’t been able to eliminate enough options. We had, as presented in the EIS, three different underground mining concepts (with different costs and constraints), and three different process flowsheet options. Sometimes you have to say: ‘we still don’t have enough data, but we know that we can make money on any of them, so we should proceed anyway..’
Nifty Copper Mine:
Little baby project to build an open pit copper mine with heap leach and Cu EW (electrowin) circuit something like 300 km east of Marble Bar in the Great Sandy Desert, 1500 km NNE of Perth (i.e, just about the most remote spot in Australia – it was really bizarre to fly for 3 hours into the desert to find there a small neat electrolytic copper production facility. As a not-really aside, the extreme remoteness was what necessitated going all the way to electrolytic cathode copper as the final product, because trucked-out concentrate would have been such a cost burden as to be a project killer.
I watched the Project Manager repeatedly re-sharpen his pencil on this little dog of a project. Too remote, not enough ore… Well, against all good judgement, the WMC board gave it the green light, it struggled into existence, they found more ore, went underground (jeez, higher costs there!) and to my amazement, it is still running, under new owners, 30 yrs later, and apparently making decent money (finding more ore, and at adequate grade, forgives lots of problems; and writing off sunk costs allow significant gains from incremental expenditures..)
Beverley Uranium:
The Beverley Project is privately owned by Heathgate Resources, itself owned by General Atomics, of Project Orion, atom bomb-powered battle-cruiser to Saturn fame…
The Beverley Project, central-eastern South Australia, is based on orebodies which reside in sand-filled palaeochannels buried at about 100 metres depth and confined by overlying (and underlying) siltstones and clays.
(Named after the wife of the original owner, Bill Siller, an entrepreneur whose mineral explorationist ‘stable’ included Exoil, Transoil, and Petromin. He had been looking for uranium in the Flinders Ranges, near the old 1930’s radium workings of Mt Painter and Radium Creek, but on prompting by his geochemist, then went looking for redeposition deposits in buried palaeochannels under the rounoff plains to the east. Wildcat drillhole number 3 or 4 hit the Beverley deposit.)
The initial mine plan (developed by then-Joint Venturer Western Nuclear, 1980) had been to open-pit the deposit. This project did not proceed for political reasons.
The project was sold in 1997, for a pittance, after Bill became fed-up with the political wrangles and delays. General Atomics decided to use the developing technology of in-situ leach, where you drill an array of boreholes, extract groundwater, add acid or alkali and oxygen, re-inject down injection wells, dissolve the uranium, and suck up through recovery wells the ‘pregnant lixiviant’ (U-loaded groundwater) which you then extract the uranium out of via solvent extraction or ion exchange.
This was to be the first acid-leach In-Situ Leach U project in Oz, thus a bit of a political adventure. The pilot plant that GA built (and that I worked on) had the U ‘just jumping out of the ground’ into our ion exchange columns! They ran the single 5-spot pattern for a year and it was still giving 50 or 60 ppm U in loaded groundwater after 11 months! We could have turned the ($5M) pilot plant into a very very lucrative commercial operation if we had had a legal pathway to get the requisite approvals.
Learning: Sometimes the Minimum Viable (commerical) Project might be very small (and very easily implemented) with very low Capex and Opex.
Arafura's Nolans Bore REE Project:
Nolans Bore is 140 km north of Alice Springs, Central Australia: Marvellous outcropping easy to mine orebody. Unfortunately, like many other REE ore, the material requires, for adequate recovery, very aggressive leaching. The project team assessed in turn, nitric, hydrochloric, and finally conc. sulphuric acid leaching (acid bake at 250 C). They at the same time, locked themselves into a complex flowsheet that sought to recover significant value from the associated phosphate, but then that rationale went away, but only after spending (wasting) $50 million on pilot testing… As a result they lost investor confidence big-time…even tho’ they gained a good handle on their process, including not just the difficult front end leaching but also the extremely painstaking differential SX separations of the 4 or 5 final RE products.