Tags: Chemical Substance, Mineral.
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 of nω=1.483 and nε=1.503.