Testing at Rubicon Minerals‘(TSX: RMX; US-OTC: RBYCF) Phoenix gold project has yielded positive reconciliation results that validate the 2018 mineral resource estimate, as well as the new geological model and structural interpretation of the F2 deposit, the company says.
Over the summer and fall, Rubicon extracted material from three test stopes in the upper areas of the deposit where modelled grades were slightly lower than the grades in the 2018 mineral resource estimate, but which were chosen because of their close proximity to substantial existing underground development.
The company extracted 35,629 tonnes (diluted) of bulk sample material from the three stopes, along with 7,260 tonnes of low-grade material, and waste material for the wet commissioning and bedding-in of the mill.
After blasting and mucking out each stope, Rubicon completed cavity monitoring surveys to assess the unplanned mining dilution from the test trial mining and recorded unplanned dilution of 8.7%, better than the company’s estimate of 10%. It was able to manage the unplanned dilution due to improved drilling and blasting techniques and mining within the deposit’s High-Ti Basalt.
The undiluted bulk sample mill results were 32,551 tonnes grading 4.93 grams gold per tonne containing 5,165 ounces of gold, which represented positive reconciliation of +7.2%, +6.1% and +13.8% compared to the 2018 mineral resource block model tonnes, grade and ounces, respectively. An accounting of gold ounces in the mill was reconciled to less than 0.5%.
Rubicon achieved 43.2% of total gold recovery from gravity separation — higher than the historical bulk sampling efforts at the project because the company was able to optimize the existing mill process. In addition, the mill operated above nameplate capacity, with a throughput rate of 1,540 tonnes per day.
“If the company could achieve these elevated levels of recovery from gravity in future mining, mill operating and processing costs would be lower as less reagents would be used,” the company states in a press release, adding that “with minor modifications, the current design and configuration of the mill could handle up to 1,800 tonnes per day, which would be beneficial for future bulk mining, if warranted.”
The successful bulk sample reconciliation gives the company “a strong foundation” to continue advancing the gold project, according to the company, and it plans to focus on upgrading resources to the measured and indicated category and growing its inferred resource.
Rubicon expects to complete an updated resource estimate in the first six months of 2019, with the addition of infill and step-out drilling completed this year and in late 2017. Once the resource is completed, it plans to complete a preliminary economic assessment.
It also intends to explore close proximity targets next year such as McFinley and its regional properties in Red Lake, Ontario.
In early afternoon trading, Rubicon’s shares were down 1¢ to $1.28 within a 52-week trading range of $1.05 and $1.88.
The company has about 66 million common shares outstanding for a market cap of $84.5 million.
Ryan Hanley of Laurentian Bank Securities has a buy rating on the company and a price target of $2.50 per share.
More than 9,000 metres of underground development has been completed on the project, including a commissioned shaft that goes down about 730 metres below surface. In addition to the mill, the project has a completed tailings management facility, electric power supply and substation and a 200-person camp.