Samarskite or properly samarskite-(Y) is a radioactive mineral with the empirical formula:

Y0.2REE0.3Fe3+0.3U0.2Nb0.8Ta0.2O4

Other formulas show Ce (cerium) rather than the generic REE (Rare earth element) and include essential titanium.

(Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16

YFe3+Nb2O8

(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. It has a Mohs hardness of 5 to 6 and a widely variable specific gravity of 4.3 - 5.87. Specimens with a high uranium content are typically metamict and appear coated with a yellow brown earthy rind. Samarskite occurs in granite pegmatites with other rare minerals.

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. Samarskite and samarium were named for the Russian mine official, Colonel Vasili Samarsky-Bykhovets (1803-1870).

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