Why this rare mineral is the primary source for the world's caesium supply

Nature · Published 3 October 2026 Swipe more like this →

In short: Pollucite is a unique zeolite mineral that serves as the planet's most significant source of caesium. While often found in lithium-rich pegmatites, the vast majority of global reserves are concentrated in a single Canadian location. Understanding this mineral reveals how specific geological formations underpin modern industrial and drilling technologies.

First identified by August Breithaupt in 1846 on the Italian island of Elba, this mineral owes its name to the mythological figure Pollux. It is frequently discovered alongside petalite, which was historically referred to as castorite, drawing a parallel to the twin of Pollux. Despite its early discovery, the mineral's true chemical potential remained hidden for years. An initial analysis conducted by Karl Friedrich Plattner in 1848 failed to detect its high caesium content, a reality that was only rectified following the formal discovery of the element in 1860. A subsequent investigation in 1864 finally confirmed the mineral's true composition.

Geologically, pollucite is a zeolite that crystallizes in the isometric-hexoctahedral system. It typically appears as colorless, white, or gray masses, though rare pink and blue varieties exist. It possesses a Mohs hardness rating of 6.5 and a density of 2.9, characterized by a brittle structure lacking cleavage. It exists in a solid solution series with analcime and is commonly found within lithium-rich granite pegmatites alongside minerals such as quartz, spodumene, and lepidolite. Well-formed crystals of this material are considered quite rare.

The economic significance of pollucite is heavily tied to a specific region in Manitoba, Canada. Approximately 82% of all known global reserves are situated near Bernic Lake. This specific ore is highly valued for its caesium content, which accounts for 23% to 25% of its total weight. The extracted material is primarily utilized in the production of caesium formate, a substance essential for assisting in oil drilling operations. This concentration of resources highlights the extreme geological specificity required to source rare elements needed for modern industrial applications.

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