Gagarinite-(Ce) previously zajacite-(Ce) is a rare radioactive

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...

mineral with formula Na( REE_''x'' Ca_1−''x'')(REE_''y''Ca_1−''y'') F₆. REE refers to rare-earth elements, mostly those belonging to the

lanthanide The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...

series. It crystallizes in the trigonal rhombohedral system and has a white vitreous appearance with a

conchoidal Conchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation. Mindat.org defines conchoidal fracture as follows: "a fracture with smooth, curved surfaces, typically sli ...

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.Webmineral data
Gagarinite-(Y) is a yttrium-rich analog. It occurs as creamy to white anhedral to subhedral grains in

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...

and aplite pods or lenses in a peralkaline igneous

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

. It was discovered in 1993 at Strange Lake, Quebec – Labrador, (56°20'N, 64°10'W) and was initially named for

Ihor Stephan Zajac Igor ( be, Ігар, Ihar ; russian: Игорь, Igor' ; sr-Cyrl, Игор ; uk, Ігор, Ihor ; ) is a common East Slavic given name derived from the Norse name Ingvar, that was brought to ancient Rus' by the Norse Varangians, in the form ...

, 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.Gagarinite-(Ce) on Mindat
Mineralienatlas in German
The new name is for Russian cosmonaut Yuri Gagarin (1934–1968).

References

Lanthanide minerals Sodium minerals Calcium minerals Fluorine minerals Trigonal minerals Minerals in space group 147 {{Halide-mineral-stub

See also

References