Zajacite or Zajacite-(Ce) is a rare radioactive fluoride mineral with formula: Na(REExCa1-x)(REEyCa1-y)F6. REE means rare earth elements mostly those belonging to the lanthanide series. It crystallizes in the trigonal - rhombohedral system It 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. It is transparent with refractive indices of nω=1.483 and nε=1.503. It occurs as creamy to white grains and phenocrysts in pegmatite and aplite pods or lenses in a peralkaline igneous intrusion.
It was discovered in 1993 at Strange Lake, Quebec - Labrador (56°20'N , 64°10'W) and was named for Dr. I. S. Zajac, who led the expedition responsible for its discovery.
Coordinates: 56°20′N 64°10′W / 56.333, -64.167
Categories: Lanthanide minerals | Sodium minerals | Calcium minerals | Halide minerals
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