Zajacite-(Ce)

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.
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General Information:
 Chemical Formula:
Na(REExCa1-x)(REEyCa1-y)F6 where (x ne y)
 Composition:
(Molecular Weight = 295.08 gm)
La,Ce,Pr,Nd,Sm,36.60 % RE
Sodium 7.79 % Na
Calcium 16.98 % Ca
Fluorine 38.63 % F 
 Empirical Formula:
NaREE0.5Ca0.5REE0.25Ca0.75F6
 Environment:
In a Precambrian peralkaline granitic complex.
 IMA Status:
Approved IMA
 Locality:
The Strange Lake rare-earth-element deposit, about 250 km northeast of Schefferville, Quebec, on the Quebec-Labrador border, Canada.
 Name Origin:
For Dr. Ihor Stephan Zajac (1935- ), the geologist who lead the exploration group that discovered the Strange Lake deposit and who first reconized the mineral.
Physical Properties:
 Cleavage:
None
 Color:
colorless, pale pink, or orange.
 Density:
4.44 - 4.55, Average = 4.49
 Diaphaniety:
Transparent
 Habits:
Granular - Generally occurs as anhedral to subhedral crystals in matrix., ,
 Hardness:
3.5 - Copper Penny
 Luminescence:
Non-fluorescent.
 Luster:
Vitreous (Glassy)
 Streak:
white
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