Gagarinite-(Ce)

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 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.[3] Gagarinite-(Y) is a yttrium-rich analog.

Gagarinite-(Ce)
General
CategoryHalide mineral
Formula
(repeating unit)		Na(REExCa1−x)(REEyCa1−y)F6
IMA symbolGag-Ce[1]
Strunz classification03.AB.35
Crystal systemTrigonal
Crystal classRhombohedral (3)
H-M symbol: (3)
Space groupP3
Unit cella = 6.099 Å, c = 11.064 Å, Z = 3
Identification
ColorColorless, pale pink, orange
Crystal habitGranular
CleavageNone
FractureConchoidal
TenacityBrittle
Mohs scale hardness3.5
LusterVitreous
DiaphaneityTransparent
Specific gravity4.44–4.55
Optical propertiesUniaxial (+)
Refractive indexnω = 1.483, nε = 1.503
Birefringenceδ = 0.020
References[2][3]

It occurs as creamy to white anhedral to subhedral grains 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 initially named for Ihor Stephan Zajac, who led the expedition responsible for its discovery, and who first recognized the presence of the new mineral. The mineral was renamed gagarinite-(Ce) in 2010 by the IMA.[2][4] The new name is for Russian cosmonaut Yuri Gagarin (1934–1968).[2]

See also

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. Gagarinite-(Ce) on Mindat.
  3. Webmineral data.
  4. Mineralienatlas in German.


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