Brazilian Critical Minerals (ASX:BCM) has reported magnesium sulphate leach assay results from 30 of 55 auger drillholes completed as part of a 100 m × 100 m resource infill drilling programme at Wellfield 1 of the Ema Ionic Rare Earth Project in Amazonas, Brazil, with the reported holes returning a combined thickness-weighted average grade of approximately 510 ppm leachable total rare earth oxides (TREO) across 219 metres of selected mineralised intervals.

Key Points

  • Top intercept EMA-TR-544 returned 8.5m at 1,062 ppm leachable TREO using magnesium sulphate leach testing above 100 ppm cut-off
  • Across 90 samples, magnet rare earth oxides (MREO) — neodymium, praseodymium, dysprosium and terbium — accounted for a highly elevated average of 43% of leachable TREO, reaching 46% in selected intervals
  • Combined dysprosium and terbium (DyTb) oxides accounted for 2–6% of leachable TREO in basal samples, with EMA-TR-537 returning 4m at 56 ppm leachable DyTb within 10m at 34 ppm leachable DyTb
  • Results are reported as complementary geological and metallurgical screening data for mine planning and are not direct predictions of field pregnant leach solution concentration or commercial recovery

Wellfield 1 Infill Drilling Programme Details

The 100 m × 100 m infill drilling programme was carried out over Wellfield 1, where the company plans to initiate the first in-situ recovery (ISR) extraction. The closer-spaced programme resolved local grade-thickness variations that previous broader 300 m to 800 m drilling did not address. The programme provided additional evidence of vertically zoned, readily leachable rare earth mineralisation hosted by weathered rhyolitic regolith, consistent with the characteristics sought in ionic-adsorption clay systems. Samples were submitted for low-strength magnesium sulphate leach analysis at 0.5M to directly characterise the soluble rare earth element fraction relevant to ISR screening. Total digestion assays were not included in this phase.

High-Grade Intercepts and Vertical Mineralisation Profile

The four strongest intercepts reported were EMA-TR-544 at 8.5m at 1,062 ppm leachable TREO, EMA-TR-535 at 8m at 1,019 ppm leachable TREO, EMA-TR-537 at 10m at 912 ppm leachable TREO, and EMA-TR-507 at 4m at 910 ppm leachable TREO. Dysprosium and terbium enrichment was observed toward the base of most holes, with the lowest sampled material geologically described as saprock hosting the highest compositions of combined DyTb. Individual samples returned up to 63 ppm combined leachable dysprosium and terbium, according to the filing. The DyTb content of 2–6% of leachable TREO represents 20–60 kg of combined DyTb oxides per tonne of leachable rare earth oxides.

Magnet Rare Earth Oxide Composition Across Reported Holes

Across 90 samples, magnet rare earth oxides accounted for a highly elevated average of 43% of leachable TREO. Selected intervals demonstrated particularly elevated magnet rare earth proportions: EMA-TR-543 from 6–12 m averaged 43% MREO; EMA-TR-544 from 0–6 m averaged 44% MREO; EMA-TR-542 from 7–16 m averaged 46% MREO; and EMA-TR-524 from 9–17 m averaged 46% MREO. Hole EMA-TR-524 also recorded magnet rare earth elements reaching up to 48% of TREO leaching values, averaging 47% from 9–16 m. The company's earlier ISR field trials demonstrated in-situ extraction of rare earths using magnesium sulphate at pH 4–4.5, with rare-earth-bearing pregnant leach solution subsequently precipitated into mixed rare earth carbonate.