Amigo Resources (LSE:AMGO) reported results from first-pass surface sampling at its Musensi Hill block in south-west Tanzania, identifying a potassium-rich alkaline volcanic unit spanning roughly 3 square kilometres within the wider 11 square kilometre licence.
The London-listed company, which is focused on gold and rare earth mining opportunities in Africa, said 43 of 54 samples from the unit returned more than 10% potassium oxide (K2O), with a median of 13.5% and a top result of 16.8%.
Musensi Hill sits within Amigo's Mbeya-Songwe licence package, where it holds a 51% interest in a joint venture targeting rare earth exploration across a recognised East African province that includes the Ngualla and Panda Hill deposits.
The potassium is hosted in leucite, a feldspathoid mineral that releases potassium into soil more readily than feldspar, a property relevant to its potential use as a remineraliser fertiliser feedstock, though no agronomic testing has been done.
Rare earth results were more localised, tied to carbonate veining cutting the volcanic unit; 14 of 54 samples exceeded 0.2% total rare earth oxide (TREO), with one isolated result of 3.76% against a median of 0.12%.
"The consistency of the potassium across this block is unusual and it is the result we are most confident in," said Craig Ransley, Amigo's executive chair, adding the rare earth signatures are "encouraging and clearly worth testing" but remain early.
The company has approved a follow-up phase of detailed mapping, ground magnetics, radiometrics and systematic sampling, with a resource drilling programme to follow subject to those results.