The update includes a M&I resource of 3.9 million tonnes grading 6.45 grams per tonne for 811,000oz contained, and an inferred resource of 2.1Mt grading 6.97g/t for 464,000oz contained at a 3g/t cut-off grade and a US$1,400/oz gold price.

"The expansion of the M&I mineral resource estimate above 800,000oz has given us the confidence to begin mine planning and engineering work at the Phoenix gold project, with the goal of demonstrating the project's commercial viability," said president and CEO George Ogilvie.

Measured gold resources increased 41% compared to the 2019 estimate, indicated resources 37% while inferred resources fell 14%, mainly as a result of the 2019 oriented infill drilling programme which aimed to improve confidence in the mineral resource estimates above the 976m level. All (M&I) mineral resources sit above this elevation. The measured resources grade fell 7%, while the indicated grade increased 5% and the inferred grade increased 7%.

The current inferred mineral resource estimate extends down to the 1,403m level, which Rubicon believes presents an opportunity to further expand the M&I mineral resource estimate at depth with additional drilling.

The company said future infill drilling had the potential to upgrade between 1-1.6Mt of mineralised material grading between 5.5-7.5g/t at depth to a mineral resource estimate. It also believes it has the potential to upgrade a portion of the 190,000oz of inferred resources between the 976m and 1,098m levels to at least the indicated category, which could be added to the feasibility mine plan. Rubicon has initiated this drilling.

Feasibility study

Work on the feasibility study among other things, will focus on upgrading the tailings management facility (TMF), including the design of an ammonia treatment plant and tailings analysis for final paste backfill design for the underground.

Rubicon has a fully operational hoist, civil and earthworks in place, electric substation and distribution system, a 200-person camp, and an existing TMF which includes a water treatment plant.

The new M&I mineral resource estimate is to the 976m depth level, well above the underground ramp bottom development of 1,403m level contemplated in the 2019 preliminary economic assessment, a level which could result in a lower total underground sustainable capital development in the feasibility study.

"I am also encouraged to see that the M&I mineral resource estimate currently only extends down to the 976m level, which could mean significantly lower sustaining capital development requirements in the mine plan of the feasibility study compared to the 2019 PEA," Ogilvie said.

Shares in Rubicon Minerals opened Tuesday almost 3% higher at C$1.05, valuing the company at $91 million.