Castillo Copper Ltd (ASX:CCZ, LSE:CCZ) has received specialist consultant ANSTO’s preliminary report on metallurgical test-work conducted on rare earth element (REE) samples from the Broken Hill Alliance (BHA) Project’s East Zone in Far West New South Wales.
Six samples from the Fence Gossan, Reefs and Tors Tanks prospects returned encouraging results, with the total rare earth element plus yttrium (TREY) grades ranging from 227 to 1,632 parts per million (ppm), consistent with earlier assay results.
Additionally, the proportion of magnetic rare earth oxide (MREO), including neodymium, praseodymium, dysprosium, and terbium, to total rare earth oxide (TREO) ranged from 22% to 27%, aligning with previous calculations.
The most successful TREY extraction, achieved through a direct leach process at pH 1, reached 30%.
BHA Project's East Zone REE discovery footprint.
Looking for improvements
Initial flotation tests on clay-hosted REE samples from Fence Gossan, Tors and Reefs Tanks prospects showed that the minerals can be separated from the clays by flotation to produce a higher-grade concentrate.
In order to further assess the extraction potential, the copper explorer appointed ANSTO to carry out metallurgical test-work on the samples.
“The board is pleased the work by ANSTO ratified the earlier assay results and high MREO to TREO ratio,” Castillo Copper chairman Ged Hall said.
“However, the board is now reviewing ANSTO’s recommendations on how to improve the metallurgical results from the BHA Project’s East Zone.”
ANSTO has recommended that CCZ include a wider variety of samples to validate the leach results and consider additional leach tests using hydrochloric acid to improve the extraction process.
Copper focus
Separately, CCZ said its geology team was close to completing an update on the 2017 mineral resource estimate for the Cangai Copper Mine in northern NSW, which will factor in results from drilling campaigns post-2017.
As well, Entech Mining is finishing the pit optimisation and mine design study for the Big One Deposit in northwest Queensland, which contains an inferred 2.1 million tonnes of copper at 1.1% for 21,886 tonnes of the metal.
“The board’s focus is now on the Australian copper assets, with critical reports due on Cangai Copper Mine and Big One Deposit that could aid materially in securing development partners,” Hall said.