Samarskite-(Y)

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Samarskite-(Y)
Samarskite-(Y)-351417.jpg
General
CategoryOxide minerals
Formula
(repeating unit)
(YFe3+Fe2+U,Th,Ca)2(Nb,Ta)2O8
Strunz classification4.DB.25
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPbcn
Unit cella = 5.687 Å, b = 4.925 Å
c = 5.21 Å; Z = 2
Identification
ColorBlack, may have a brownish tint, brown to yellowish brown due to alteration; light to dark brown in transmitted light
Crystal habitCrystals elongated with pyramidal terminations; commonly granular to massive
Cleavage{010}, indistinct
FractureConchoidal fragments
TenacityBrittle
Mohs scale hardness5 - 6
LusterVitreous - resinous
StreakReddish brown
DiaphaneityOpaque, transparent in thin fragments
Density5.6 - 5.8, Average = 5.69
Optical propertiesAppears isotropic
Refractive indexn = 2.1–2.2
Alters toMetamict
Other characteristicsRadioactive (Greater than 70 Bq / gram)
References[1][2][3][4]

Samarskite is a radioactive rare earth mineral series which includes samarskite-(Y) with formula: (YFe3+Fe2+U,Th,Ca)2(Nb,Ta)2O8[2] and samarskite-(Yb) with formula (YbFe3+)2(Nb,Ta)2O8.[5] The formula for samarskite-(Y) is also given as: (Y,Fe3+,U)(Nb,Ta)O4.[4]

Samarskite crystallizes in the orthorhombic - dipyramidal class as black to yellowish brown stubby prisms although it is typically found as anhedral masses. Specimens with a high uranium content are typically metamict and appear coated with a yellow brown earthy rind.

Samarskite occurs in rare earth bearing granite pegmatites with other rare minerals. It occurs in association with columbite, zircon, monazite, uraninite, aeschynite, magnetite, albite, topaz, beryl, garnet, muscovite and biotite.[4]

Samarskite was first described in 1847 for an occurrence in Miass, Ilmen Mountains, Southern Ural Mountains of Russia.[3] The chemical element samarium was first isolated from a specimen of samarskite in 1879. Samarium was named after samarskite which was named for the Russian mine official, Colonel Vasili Samarsky-Bykhovets (1803–1870).[3]

Samarskite-(Yb) was first described in 2004 for an occurrence in the South Platte Pegmatite District, Jefferson County, Colorado.[5][6]

Samarskite specimen, broken to show fresh surface

See also[edit]

References[edit]