The company said the mix of surface and underground mining
offer "significant upside" from economies of scale.
It has already allowed the junior the chance to boost its reserves by 63% to 7.48 million tonnes grading 0.15% for 12,374t of contained tungsten.
The wider project comes with a near-surface exploration target of between 25,000t and 112,000t tungsten.
Managing director Steven Turner said the PFS shows its plans to redevelop Santa Comba, which last produced in 1985, are economically robust.
A pit-only scenario delivers a pre-tax net present value of A$95 million and an internal rate of return of 33%.
Payback of the $53 million capital cost is put at just over two years following commissioning.
Net profit is estimated at $93.6 million based on reserves only, but management also studied inclusion of 445t of inferred resources that could boost profitability to $115 million.
The pit would operate at a mining rate of 1.3Mtpa over seven years, with two years required for construction and commissioning. Three years would be required to ramp up production to target.
Annual production from two pits is expected to be 2167t of calcium tungstate grading 63% tungsten. The product is expected to fetch a premium from buyers over tungsten concentrate.
A further 1Mtpa of aggregates from mine waste would also be processed over 15 years.
Rafaella is now finalising minor aspects of definitive feasibility study, including some metallurgical optimisation studies.
Turner said the advanced PFS was sufficiently encouraging to support its application for designation as a strategic industrial project, which would help facilitate an acceleration of permitting of the open pit.
Its underground operation is based on an inferred resource of 2752t tungsten and 662t tin and is already permitted.
It is already operating a pilot plant at Santa Comba, processing high-grade stockpiles.
Assuming pit permitting can be secured in 2023, it aims to be in production by early 2026.
Exploration efforts in tandem may allow reserves and resources to grow, given just 10% of the mining licence has been properly explored.
It acquired the mine in January.
The fully permitted San Finx produced 32t of wolframite concentrate and 35t of tin concentrate for sale in 2017, but development ceased due to a need to secure a water permit required to access deeper levels of the orebody.
It hopes to have San Finx back in production by 2024.
Rafaella started the quarter with $1.8 million in cash.
Shares in the company rose 6% today to 3.6c, valuing it at $8 million.
The stock has traded at 2.8-11c over the past year.