Samarskite

samarskite [sə′mär‚skīt]

(mineralogy)

(Y,Ce,U,Ca,Fe,Pb,Th)(Nb,Ta,Ti,Sn)₂O₆A velvet-black to brown metamict orthorhombic mineral with splendent vitreous to resinous luster occurring in granite pegmatites. Also known as ampangabeite; uranotantalite.

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Samarskite 

(named in honor of the Russian mining engineer V. E. Samarskii-Bykhovets [1803–70]), a mineral of the class of oxides, a tantaloniobate of rare-earth elements with the approximate chemical formula (Y, U, Fe)₂(Nb, Ti, Ta)₂O₆. There are several varieties of samarskite, including calcio-samarskite, which contains Ca; khlopinite, which is enriched with Ti; and ishikawaite, which is rich in U. Samarskite crystallizes in the rhombic system, and the crystals have a prismatic habit. The regular coalescence of samarskite with columbite (ánnerödite) is characteristic.

Samarskite is found primarily in a metamict state. It forms irregular grains and accumulations and has a velvet-black color with a clear tarry luster. Brown or yellowish brown incrustations are characteristically present. Samarskite has a hardness of 5–6 on Mohs’ scale, and its density varies depending on chemical composition from 5,600 to 5,800 kg/m³. Samarskite is commonly associated with monazite, zircon, uraninite, columbite, magnetite, topaz, and beryl. It serves as an ore for the extraction of uranium.

Samarskite is found in granite pegmatites in various areas of the USSR, including the Urals, the Ukraine, and Middle Asia. Samarskite is also found in Norway (Hitteröy, Ånneröd), Sweden, the Malagasy Republic, India, Japan, Brazil, and the USA.