Samarskite-(Y)

Samarskite is a radioactive rare earth mineral series which includes samarskite-(Y), with the chemical formula (YFe³⁺Fe²⁺U,Th,Ca)₂(Nb,Ta)₂O₈^[3] and samarskite-(Yb), with the chemical formula (YbFe³⁺)₂(Nb,Ta)₂O₈.^[6] The formula for samarskite-(Y) is also given as (Y,Fe³⁺,U)(Nb,Ta)O₄.^[5]

Samarskite-(Y)
General
Category	Oxide minerals
Formula	(YFe3+Fe2+U,Th,Ca)2(Nb,Ta)2O8
IMA symbol	Smk-Y[1]
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
Identification
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	[2][3][4][5]

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.^[5]

Samarskite was first described in 1847 for an occurrence in Miass, Ilmen Mountains, Southern Ural Mountains of Russia.^[4] 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).^[4]

Samarskite-(Yb) was first described in 2004 for an occurrence in the South Platte Pegmatite District, Jefferson County, Colorado.^[6][7]

Samarskite specimen, broken to show fresh surface

See also

• Decipium, a mis-identified new element, thought to have been extracted from samarskite in 1878 by Marc Delafontaine.
• List of minerals
• List of minerals named after people