Geographic Minerals



Gagarinite-(Ce) previously zajacite-(Ce) is a rare radioactive fluoride mineral with formula Na(REExCa1-x)(REEyCa1-y)F6. REE refers to rare-earth elements, mostly those belonging to the lanthanide series. It was discovered in 1993 at Strange Lake, Quebec – Labrador, (56°20’N, 64°10’W) and was initially named for Ihor Stephan Zajac, who led the expedition responsible for its discovery, and who first recognized the presence of the new mineral.

General Information

  • Category: Halide mineral
  • Formula: Na(REExCa1-x)(REEyCa1-y)F6
  • Crystal system: Trigonal
  • Crystal class: Rhombohedral (3)

Fig: Gagarinite-(Ce)


It crystallizes in the trigonal rhombohedral system and has a white vitreous appearance with a conchoidal fracture. It has a Mohs hardness of 3.5 and a specific gravity of 4.44 to 4.55. Zajacite is transparent with refractive indices nω = 1.483 and nε = 1.503. Gagarinite-(Y) is a yttrium-rich analog.

  • Color: Colorless, pale pink, orange
  • Crystal habit: Granular
  • Fracture: Conchoidal
  • Tenacity: Brittle
  • Mohs scale hardness: 3.5
  • Luster: Vitreous
  • Diaphaneity: Transparent
  • Specific gravity: 4.44–4.55
  • Optical properties: Uniaxial (+)


It occurs as creamy to white anhedral to subhedral grains in pegmatite and aplite pods or lenses in a peralkaline igneous intrusion. The mineral was renamed gagarinite-(Ce) in 2010 by the IMA. The new name is for Russian cosmonaut Yuri Gagarin (1934–1968).

Occurrence: In a rare-earth-element enriched, peralkaline granitic complex (Strange Lake).

Association: Vlasovite, narsarsukite, willemite, fluorite (Strange lake).

Distribution: From the Strange Lake deposit, Quebec-Labrador, Canada


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