Samarium

samarium

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Symbol: Sm
Lanthanide and rare earth metal.
Samarium is not found free in nature but is found in a number of minerals mainly monazite and bastnäsite (monazite-(Sm) is an approved mineral species; there is no approved "bastnäsite-(Sm)", but samarium may be found as an impurity in other bastnäsite species). In its compounds samarium usually exists as a trivalent ion, Sm³⁺, but it may also exist as the divalent ion Sm²⁺.
Crystal system: Hexagonal
Specific gravity: 7.54
Colour: Silvery white
Stability: Stable in air at normal temperatures, but ignites in air when the temperature is 150^oC or higher. In moist air it tarnishes to the oxide.
Melting point: 1170^oC
Boiling point: 1790^oC
Abundance in the Earth's crust: 6 parts per million by mass, 0.8 parts per million by moles (ChC).
Abundance in the Solar System: 1 part per billion by mass, 10 parts per trillion by moles (ChC).
Samarium-bearing minerals include:

Carbonates
kozoite-(Nd)*
schuilingite-(Nd)*
shabaite-(Nd)*

Phosphates
florencite-(Sm)
françoisite-(Nd)*
monazite-(Sm)

Sorosilicates
allanite-(Sm)

*The IMF formula does not contain Sm, the Mindat formula contains Sm replacing some Nd.


Carbonates - the carbonate anion is (CO₃)^2-
Phosphates - the phosphate anion is (P⁵⁺O₄)^3-
Sorosilicate - (Si⁴⁺₂O₇)^6- groups

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