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Category Oxide minerals
(repeating unit)
Strunz classification 4.DB.25
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pbcn
Unit cell a = 5.687 Å, b = 4.925 Å
c = 5.21 Å; Z = 2
Color Black, may have a brownish tint, brown to yellowish brown due to alteration; light to dark brown in transmitted light
Crystal habit Crystals elongated with pyramidal terminations; commonly granular to massive
Cleavage {010}, indistinct
Fracture Conchoidal fragments
Tenacity Brittle
Mohs scale hardness 5 - 6
Luster Vitreous - resinous
Streak Reddish brown
Diaphaneity Opaque, transparent in thin fragments
Density 5.6 - 5.8, Average = 5.69
Optical properties Appears isotropic
Refractive index n = 2.1–2.2
Alters to Metamict
Other characteristics Radioactive (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]