Samarskite-(Y)

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)5O16YFe3+Nb2O8(Y,Fe3+,U)(Nb,Ta)O4Samarskite 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.
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General Information:
 Chemical Formula:
(Y,Fe+++,U)(Nb,Ta)5O4
 IMA Status:
Approved IMA 1987
 Name Origin:
The element samarium (Sm) was named after this mineral.
Physical Properties:
 Cleavage:
[???] Imperfect
 Color:
black, brownish, or yellowish brown.
 Density:
5.6 - 5.8, Average = 5.69
 Diaphaniety:
Opaque
 Habits:
Massive - Uniformly indistinguishable crystals forming large masses., ,
 Hardness:
5-6 - Between Apatite and Orthoclase
 Luminescence:
Non-fluorescent.
 Luster:
Vitreous - Resinous
 Streak:
reddish brown
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