Pollucite
A zeolite mineral and major caesium ore.
Pollucite is a zeolite mineral with the formula (Cs,Na)2Al2Si4O12·2H2O, notable as a significant ore of caesium and sometimes rubidium. It forms a solid solution series with analcime and crystallizes in the isometric-hexoctahedral crystal system as colorless, white, gray, or rarely pink and blue masses.
- formula
- (Cs,Na)2Al2Si4O12·2H2O
- crystal_system
- isometric-hexoctahedral
- hardness
- 6.5
- specific_gravity
- 2.9
- color
- colorless, white, gray, rarely pink and blue
- cleavage
- none
- fracture
- brittle
Lore & Background
It is named for Pollux, the twin of Castor, because it is often found associated with petalite (previously known as castorite). Its typical occurrence is in lithium-rich granite pegmatites in association with quartz, spodumene, petalite, amblygonite, lepidolite, elbaite, cassiterite, columbite, apatite, eucryptite, muscovite, albite and microcline. About 82% of the world's known reserves of pollucite occur near Bernic Lake in Manitoba, Canada, where they are mined for their caesium content for use in caesium formate oil drilling assistance. This ore is about 23% to 25% caesium by weight.
Reader's Guide
Pollucite holds significance as a primary ore of caesium, a metal used in specialized applications such as caesium formate for oil drilling assistance. The mineral's association with lithium-rich pegmatites and its solid solution series with analcime provide insights into geological processes. Economically, the concentration of global reserves near Bernic Lake, Manitoba, makes this deposit critical for caesium supply. The mineral's physical properties—hardness of 6.5, specific gravity of 2.9, brittle fracture, and lack of cleavage—aid in its identification. Its naming after Pollux, twin of Castor, reflects its common association with petalite (castorite).
Did You Know?
- Pollucite is named for Pollux, the twin of Castor, because it is often found associated with petalite (previously known as castorite).
- About 82% of the world's known reserves of pollucite occur near Bernic Lake in Manitoba, Canada.
- Pollucite ore from Bernic Lake is about 23% to 25% caesium by weight.
Frequently Asked Questions
What is Pollucite?
Pollucite is a zeolite-group mineral best known as the principal natural ore of caesium, with occasional rubidium recovery as a byproduct. It is listed as entry 1-24 in the Minerals & Ore Deposits series.
What is Pollucite's chemical formula and how does it relate to other minerals?
Its composition is (Cs,Na)2Al2Si4O12·2H2O, meaning caesium and sodium substitute for one another in the lattice. This allows it to form a continuous solid-solution series with the closely related zeolite analcime.
What crystal system does Pollucite belong to and what are its physical properties?
It crystallizes in the isometric-hexoctahedral system, typically as massive aggregates rather than discrete crystals. Its Mohs hardness is 6.5, specific gravity is 2.9, and it exhibits no cleavage.
What colors can Pollucite appear in?
The vast majority of specimens are colorless, white, or gray, while pink and blue hues are noted as rare variants. These subtle color shifts make unusual specimens a particular draw for collectors.
Why is Pollucite important to industry and mineral enthusiasts?
It is the chief source of caesium, a metal critical to atomic clocks and specialty optics, giving it outsized economic value relative to most zeolites. For hobbyists, its rarity as a caesium-bearing species combined with occasional unexpected coloration makes it a prized cabinet piece.
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