While the preliminary economic assessment is still being completed by consultants IHC Mining, the engineering study over the Koko Massava, Nhacutse, and Poiombo deposits suggests the development can access 513 million tonnes of mining inventory at a processing rate of 20.1Mtpa.
Capital costs are put at US$239 million.
The pits require no stripping, and the resources are described as "strongly homogeneous" with favourable heavy mineral sands gain size and easy clay fines removal characteristics, which should deliver a low-cost processing flowsheet, with all-in operating costs of $3.05/t via the proposed port at Chongoene, just 40km away.
The first three years should deliver an average processing grade of almost 6.5% total heavy minerals, and by year 15 it should still exceed 5% THM.
Indicative production over the 25-year mine life could deliver some 383,000t Ilmenite, 273,000t titanomagnetite concentrate, and 50,000t of non-magnetic concentrate.
The value of production will be indicated by the PEA for a higher-grade starter project.
IHC is completing tests on a 6.5t bulk sample and the results will inform final product specifications and is the final piece of work for the PEA.
MRG chair Andrew Van Der Zwan said the engineering scoping study gave the company comfort it had what should be a robust, world-class mineral sands project, developing three deposits that are each about 4km apart.
Resources at Corridor exceed 1Bt, and there is an exploration target of up to a further 500Mt.
Recent aircore drilling of three targets at the nearby Marao project has also returned support there are more mineral sands at similar grades to Koko Massava.
MRG has also applied for three new tenements some 780km north-east of the Corridor project, with potential for rare earth elements and uranium.
The junior had A$1 million in cash and equivalents at the end of the June quarter.
MRG shares were up 14% yesterday at 0.8c, capitalising it at $14 million.
It has traded at 0.6-0.15c over the past year.
