Drilling over the past year has allowed it to grow its total resource across the Red Tail and Yellow Tail deposits by 104% to 81.4 million tonnes at 785 parts per million total rare earth oxides.
The grade has also increased 15% from the April 2021 resource.
Just over half the resource has also been converted into a maiden indicated resource of 45Mt at 835ppm TREO.
The company said it was well on the path to establishing a globally significant inventory at Koppamurra, and was in a position to start strategic discussions with critical minerals end-users who are looking for a source of the critical minerals from outside China.
Managing director Don Hyma said the project, which spans the SA-Victorian border, is firming as a "unique rare earth business opportunity" given it is dominated by the high value neodymium, praseodymium, dysprosium and terbium elements.
It has already sparked a land rush in the area, with explorers such as Lanthanein Resources (previously Frontier Resources) and Resource Base moving in and defining REE mineralisation of their own.
Hyma said the Koppamurra deposits were proving to be consistent, enabling expedient drilling and rapid resource growth for what could be a mining and processing operation that lasts for decades.
The shallow, free-digging nature of the mineralisation also provides the ability to undertake progressive rehabilitation.
The average hole depth is just 10m.
"This outstanding result is a game-changer because it elevates Koppamurra to the stage where its future as a significant project is now clear," he said.
"Koppamurra is one of only three advanced ionic clay-hosted rare earth deposits outside China/Myanmar, and it is now emerging as a project of both scale and quality."
Development options for Koppamurra are expected to be modular and low cost, with the company seeking to establish production in 2025-26.
Drilling to date covers just 5% of the 4000sq.km project area.
An exploration target for the adjoining area of 90-220Mt grading 629-849ppm has been defined and will be a focus for drilling over the next year, infilling spacings that are 1-2km wide.
Technical and metallurgical studies are ongoing to confirm that the key magnet inputs can be economically recovered. A pilot plant is planned once lab tests are complete.
AR3 is planning to drill between 10,000-20,000m starting later this quarter to upgrade its resources further.
The company recently raised A$8 million at 44c, adding to its cash at the start of the June quarter of $7 million.
AR3 listed on July 1, 2021 following a $12 million IPO that issued shares at 30c each.
The stock, which has traded between 30c and $1.35, was up 13% this morning to 42c, valuing it at almost $50 million.
