The MoU follows an agreement RareX struck with KMG Logistics to share the latter's bulk logistics facility at Wyndham port.
Nitron has expressed interest in 250,000 tonnes of Cummins Range stage 1 pre-strip direct shipping ore phosphate and 250,000t of stage 2 mineral concentrate.
Stage 1 ore grades 25% phosphate while stage 2 concentrate grades 32% phosphate.
Currently, 32% phosphate ore is fetching about $538/t.
The stage 2 concentrate product can be produced through RareX's proposed beneficiation plant, using low-grade rare earths blocks within the Cummins Range orebody.
RareX chief executive officer James Durrant said the MoU marked another material step towards de-risking Cummins Range's product and project development strategy.
"We are very pleased to have Nitron on board as a potential future offtake partner for our product sales," he said.
According to a scoping study done in August, Cummins Range can give up 300,000t per annum of phosphate from pre-strip for three years, before moving to a dual mineral concentrate product of rare earth and phosphate minerals.
Durrant said the ability to sell some of the pre-strip material as a standalone product meant there was a low-risk start-up pathway for the project and the supply chain before it became a full project with the installation of a beneficiation plant.
"The benefits of this low-risk development pathway to deliver a critical minerals rare earth project should not be understated," he said.
"It makes Cummins Range fundable, executable and operatable and, once the beneficiation plant is installed, we'll be in a position to produce more rare earths for less capital expenditure than any of our peers."