Dateline Resources has wrapped a net present value of US$235m around its Colosseum gold project in California that is set to churn out 635,000 ounces over 8.3 years at an AISC per ounce of US$1490. That number compares favourably to today’s gold price US$2752 an ounce or AUD$4121 an ounce. Dateline will bank a total of US$1.344b in sales over the life of mine with about US$400m of that dropping to the bottom line as net revenue.
The figures are contained in a freshly tabled scoping study on the project that is based in San Bernardino County, California, confirming the historic mine still has plenty of legs left in it.
The study is based on Dateline’s June mineral resource estimate and has been endorsed by the Board and approved for progression to the project selection stage ahead of a bankable feasibility study.
The Colosseum gold mine is located at the southern section of the Walker Lane Trend about 80km southwest of Las Vegas.
The Walker Lane Trend hosts numerous substantial discoveries, including the 1.7 million ounce Mother Lode Deposit and the 6.5 million ounce Castle Mountain gold mine.
The Colosseum mine lies within the old Clark Mountain mining district, which has produced silver, gold, copper, lead, tungsten and fluorite at various times over the last 120 years, while gold was first produced in the district in the 1930s.
In the late 1800s, the Colosseum Mine produced about $18,000 worth of gold and silver but it was expanded greatly during the 1980s and 1990s when mining technology improved.
During its most productive years, the operation yielded more than $100 million worth of gold and silver from two open pits, the South Pit and the North Pit.
In the 1970s, Draco Mines and its partners performed intermittent exploration drilling on the Colosseum property before Amselco leased the property from Draco in 1982 and undertook extensive drilling and feasibility studies between 1982 and 1984.
Dallhold Resources purchased the Colosseum property in September 1986 before it became part of Alan Bond’s Bond International Gold and mine and mill construction began in 1987, with the mill beginning operations in January 1988.
In 1989, Canadian miner LAC Minerals acquired the project by taking over Bond and operated the mine from 1989 to 1993 with production from the two pits for just 4.5 years out of the initially planned 9 years.
By July 1990, Colosseum Inc, a subsidiary of Lac Minerals, had produced more than 170,000 ounces of gold from the operation, but Lac ceased mining in July 1992 after four and a half years of operation, although milling of stockpiled ore continued until mine closure in May 1993.
The gold price was below US$350 (A$525)/per ounce when the Colosseum mine stopped production.
In 1994, Barrick Gold made a successful takeover bid for LAC and Barrick held the Colosseum project for almost two decades with little work being done, believing then that only 300,000 ounces were left in reserves and the operation was too small to pursue.
Dateline acquired the Colosseum mine from Barrick in 2021, when Barrick was rationalising its non-core assets and promptly committed to the project’s first modern exploration and development program, reviewing all available exploration and production data and compiling a new digital database for both exploration planning and mineral resource modelling.
Dateline also set about redefining the resource and bringing it up to a 2012 JORC standard of 813,000 ounces in 2022, after which additional drilling earlier this year lifted the global resource estimate to 1.1 million ounces. 736,000 of those ounces lie in the combined measured and indicated category at a grade of 1.26g/t gold.
Two long diamond core runs in the North Pipe resulted in a 203.6m hit grading 1.03g/t gold and 192m running at 1g/t, including a reported high-grade section of 8.17g/t gold.
The scoping study has examined two possible early options after bench-marking its possible production and development options against 16 projects using published information for capital costs and on 38 projects for operating costs.
The first case (Case 1) option contemplates a 1 million tonne per year combined underground and open pit operation, with sub-level caving followed by open pit mining.
The second – and preferred case - Case 2 - considers a 2 million tonne per year open pit mine, based on the combined measured and indicated mineral resources accounting for 81 per cent of the mill-feed.
The Case 2 mine plan involves open pit cutbacks of both the South pipe and North pipe at Colosseum.
Additionally, the proposed processing flowsheet envisions a scaled-up version of the carbon-in-pulp (CIP) processing plant which operated at Colosseum during Lac’s 1989-1993 tenure, essentially doubling the throughput which would not only meet the 2 million tonne per year processing objective but which Dateline figures will fit in the approved operational area.
The Case 2 modelling contemplates an operation to mine and process 16.55 million tonnes of ore from both open-pits at an average head-grade of 1.30g/t gold to produce 635,000 ounces of gold – just over 75,000 ounces per year - at an assumed gold price of US$2200 per ounce of gold, over an initial 8.3 year mine life.
The South Pit remains as a 130m deep void with the bottom 26metres flooded to the standing groundwater level. Mining in the North Pit was suspended before it went substantially below ground level, so all the benches are still open out onto the western slope of the range.
The total material movement would be 73.3 million tonnes which includes the corresponding 56.75 million tonnes of waste, for a solid overall strip ratio of 3.4:1.
Plant throughput is averaged at 1.8 million tonnes per year and recovery is gauged at 92 per cent, yielding a net gold production of 635,000 ounces.
Total CAPEX for the project came in at US$195 (A$292) million, however pre-production CAPEX is only US$138 (A$207) million and a further US$15m (AUD$25m) in working capital is needed.
The project’s future would appear to be assured – particularly in light of the current seemingly irrepressible gold price.
Importantly, results from recent drilling at North Pipe and with South Pipe show potential depth extensions beyond the current mineral resource block, both of which represent mine life growth potential, subject to additional infill, extensional and resource conversion drilling.
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By Doug Bright
