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Samarskite
Chemical Formula	(YFe3+Fe2+U,Th,Ca)2(Nb,Ta)2O8
Species	Oxides & Hydroxides
Crystal System	Orthorhombic
Mohs Scale	5-6
Color	Black, may have a brownish tint, brown to yellowish brown due to alteration; light to dark brown in transmitted light
Streak	Reddish brown
Luster	Vitreous - resinous
Refractive Index	n = 2.1–2.2
Diaphaneity	Opaque, transparent in thin fragments
Cleavage	, indistinct
Fracture	Conchoidal fragments
Crystal Habit：Crystals elongated with pyramidal terminations; commonly granular to massive

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

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.

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

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