Dual-listed Patriot Battery Metals on Monday confirmed a major caesium discovery at its Shaakichiuwaanaan project in Quebec, with new resource estimates positioning the Rigel and Vega zones as the "world’s largest pollucite-hosted caesium pegmatite deposit".

The rare and high-value critical mineral is increasingly sought for its role in next-generation solar technologies.

The company unveiled a maiden mineral resource estimate (MRE) for caesium within the CV13 pegmatite, with Rigel and Vega zones collectively containing 30 500 t of cesium oxide (Cs₂O) in the indicated category and 40 800 t inferred, significantly outpacing any known pollucite-hosted deposits globally.

“At Shaakichiuwaanaan, we have now defined the largest reported occurrence of pollucite in the world – by a significant margin,” said Patriot executive and exploration VP Darren Smith. “To find a pollucite-hosted caesium deposit of this scale and grade is exceptionally rare, with only three deposits globally known to have produced this extremely high-value critical and strategic mineral.”

The Rigel zone MRE stands at 163 000 t grading 10.25% Cs₂O, while the Vega zone hosts 530 000 t at 2.61% Cs₂O (indicated) and 1.7-million tonnes at 2.40% Cs₂O (inferred). These grades position the discovery well above historical pollucite production benchmarks, such as the Sinclair mine in Australia, which yielded just over 1 500 t of contained Cs₂O before depletion in 2019.

“This is another feather in the cap of our technical team,” said Patriot president, CEO and MD Ken Brinsden. “What stands out is the sheer scale and grade of this caesium discovery, relative to anything that’s been found before globally.”

Pollucite, the primary mineral host for caesium, is geologically rare and economically significant, particularly as supply options dwindle. Only three pollucite-hosted caesium mines have historically operated –Tanco, in Canada, Sinclair, in Australia, and Bikita, in Zimbabwe – and all are now either depleted or nearing end-of-life.

“What is particularly exciting for investors is that the addressable market for caesium appears to be at a key inflexion point, with its ability to improve the efficiency and stability of next generation terrestrial solar technologies having the potential to drive a massive increase in global demand," highlighted Brinsden.

Caesium has traditionally been used in oil and gas drilling fluids, catalysis, and medical imaging. However, its role in enhancing the performance of perovskite-based solar panels is now attracting growing industry interest. High-purity caesium carbonate (≥99%) currently fetches around $120/kg, while metallic caesium (≥99.5%) trades at $2 540/oz ($81/g), placing it among the highest-value metals globally.

The discovery is hosted within the CV13 pegmatite, part of the company’s consolidated MRE that now totals 108-million tonnes (indicated) at 1.40% lithium oxide (Li₂O) and 0.11% Cs₂O, and 33.4-million tonnes (inferred) at 1.33% Li₂O and 0.21% Cs₂O.

Patriot Battery Metals has begun evaluating potential metallurgical pathways to commercially recover pollucite using conventional ore sorting methods. The company plans to advance the caesium opportunity in tandem with its lithium strategy, following the expected third quarter completion of a lithium-only feasibility study for the CV5 pegmatite.

“With considerable mineral resources for lithium, tantalum, gallium, and now caesium defined . . . the company is becoming increasingly well-positioned as an emerging critical minerals powerhouse to global markets,” said Smith.

The Shaakichiuwaanaan project is located in Quebec’s Eeyou Istchee James Bay region and is accessible by all-season road. The CV13 pegmatite lies about 3 km west of the CV5 pegmatite and 13 km south of the Trans-Taiga Road and powerline corridor, positioning the project advantageously for development and potential production.