Gagarinite-(Ce)

Gagarinite-(Ce) previously zajacite-(Ce) is a rare radioactive fluoride mineral with formula Na(REE_xCa_1−x)(REE_yCa_1−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 n_ω = 1.483 and n_ε = 1.503.^[3] Gagarinite-(Y) is a yttrium-rich analog.

Gagarinite-(Ce)
General
Category	Halide mineral
Formula (repeating unit)	Na(REExCa1−x)(REEyCa1−y)F6
IMA symbol	Gag-Ce^[1]
Strunz classification	03.AB.35
Crystal system	Trigonal
Crystal class	Rhombohedral (3) H-M symbol: (3)
Space group	P3
Unit cell	a = 6.099 Å, c = 11.064 Å, Z = 3
Identification
Color	Colorless, pale pink, orange
Crystal habit	Granular
Cleavage	None
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	3.5
Luster	Vitreous
Diaphaneity	Transparent
Specific gravity	4.44–4.55
Optical properties	Uniaxial (+)
Refractive index	nω = 1.483, nε = 1.503
Birefringence	δ = 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

• List of minerals
• List of minerals named after people

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.