The 9,000-metre program will test shallow neodymium-praseodymium (NdPr) mineralisation identified across the six square kilometres of Longonjo carbonatite.
This is less than 30 metres deep and is open in all directions.
Rift Valley chief operating officer Dave Hammond said it had been a great team effort to allow the drilling to start on schedule.
He said: “We are targeting a large tonnage, high-grade deposit that could rank Longonjo as one of the world’s biggest NdPr projects.
“[We] are really looking forward to reporting the first results within the next few weeks.”
The first drill hole was started this week and has so far intersected a 24-metre-deep weathered zone.
Longonjo contains a large new discovery of NdPr mineralisation that is part of the 11.6 million tonnes at 4.30% rare earth oxide JORC maiden resource.
It is adjacent to the $1.8 billion rail link to the Port of Benguela on the Atlantic coast and 4.3 kilometres from the sealed national highway.
A power transmission line from the Gove Dam hydroelectric power plant extends to Caala, 38 kilometres east of the project.
After completing the RC program, Rift Valley will begin a second phase of RC as well as diamond drilling to infill areas of high-quality NdPr mineralisation.
This will be accompanied by mineralogical and metallurgical evaluation programs to test potential processing methods.
The focus on Longonjo comes at a time when demand for NdPr is set to soar as a vital component in electric motors.
The permanent magnet motor market is projected to grow from US$26.6 billion in 2017 to US$48.3 billion in 2023, representing a compound annual growth rate of 10.47%.
China dominates the market with over 95% of NdPr metal production.
Prices of the feedstock NdPr oxide have risen to $53,000 per tonne and are forecast to continue rising as NdPr magnets are targeted in the US-China trade war and demand outstrips supply.