Key highlights

• Alvo Minerals is targeting a maiden mineral resource estimate for its Boa Vista heavy rare earths prospect in 2027.

• Auger drilling extended mineralisation two kilometres south and west, with depth now the key point of the results.

• The Boa Vista prospect is part of the Bluebush ionic adsorption clay heavy rare earth element project.

Alvo Minerals (ASX:ALV) is targeting a maiden mineral resource estimate in 2027 after auger drilling extended mineralisation at the Boa Vista prospect two kilometres to the south and west. The prospect is part of the Bluebush Ionic Adsorption Clay Heavy Rare Earth Element Project in Tocantins, Brazil. Alvo reported the results to the ASX on 2 November.

The company released assays from 42 auger holes drilled on newly acquired ground on a nominal 300-metre grid across about 6.5 square kilometres. The holes totalled 170.6 metres and produced 176 samples.

The headline numbers

Fifteen holes returned intercepts above a 750 ppm total rare earth oxide (TREO) cut-off, with heavy rare earth oxides averaging 19% of TREO. Magnet and heavy rare earths together accounted for 37%.

Hole BLG0358 returned 10 metres at 1,364 ppm TREO, including 6 metres at 1,527 ppm with 45 ppm dysprosium and terbium. BLG0360 returned 8 metres at 1,291 ppm TREO from surface, and BLH0101 returned 5 metres at 1,152 ppm from three metres.

Why depth is the key point

The answer to the headline question is that grades appear to rise with depth. Across the batch, dysprosium and terbium nearly tripled from 13 ppm at surface to 35 ppm below seven metres. The magnet rare earth share of TREO climbed from about 16% in the upper two metres to 24% below five metres.

Most holes ended in mineralisation. Diamond drilling at Boa Vista shows the saprolite profile averages about 20 metres before fresh granite, while the auger holes averaged only about four metres, based on the reported totals. That suggests the augers stopped well short of the full clay thickness, and that the better-grade lower parts of the profile have not been fully sampled.

Alvo intends to redrill several auger holes. If deeper drilling confirms higher grades through a thicker profile, it could have a significant effect on any future resource. That remains to be tested.

An unusual high-grade sample

One hole, BLH0115, ended at auger refusal in saprock and returned 0.5 metres at 4,259 ppm TREO and 138 ppm dysprosium-terbium. Alvo said the grade may reflect a primary mineral rather than clay-adsorbed rare earths, and has prioritised the interval for desorption testing.

That distinction matters. The appeal of ionic clay deposits is that rare earths can often be recovered with mild leaching. Rare earths locked in primary minerals typically need harsher processing.

Supporting geophysics

The results reconcile with a portable electromagnetic survey reported on 27 October, with deeper, higher-grade holes sitting over the strongest clay response. That correlation could help target future drilling.

Market context

Alvo highlighted widening premiums for heavy rare earths outside China. It said that by late September, dysprosium oxide was trading at about 16 times Chinese domestic prices, terbium about seven times and yttrium more than 150 times. Those are the company's figures, and such premiums can change quickly with policy.

Funding and caveats

Auger drilling is a low-cost first-pass method, and no resource exists yet.

What to watch

Investors may watch for deeper drilling, desorption test results and progress towards the 2027 estimate.

Ionic clays in context

Ionic adsorption clay deposits in southern China have long been the world's main source of heavy rare earths, which is why similar deposits elsewhere attract attention. Brazil has emerged as a focus for such exploration, with several ASX-listed companies active there. The challenge is that grades and leachability vary widely, and environmental management of leaching operations is closely scrutinised. Alvo's desorption tests and deeper drilling will be the key evidence for how its project compares. Those results will shape resource work.