Perhaps one of the most interesting things to note about samarium is that it has a total of seven different naturally occurring isotopes. Again, as a quick recap for the casual enthusiast, the number of protons in an atom determine its chemistry and is what separates one element from another. The number of neutrons on the other hand may vary and this alters its mass slightly and may affect the atom’s stability (turning it radioactive and therefore prone to decay). Of samarium’s seven isotopes, two are ever so slightly radioactive. Much too low to be directly detectable with a Geiger counter, this radioactivity has been determined through computational analyses of the atomic structure. So no need to skip this one on account of it being dangerous.

Of the 14 rare earth elements that make up the lanthanide series (not counting promethium) five are too reactive to remain in their elemental state in open air and must be kept in oil, or preferably sealed in glass with argon. Samarium is a borderline number six. Shiny just after completing the last processing steps at the lab, it begins to tarnish slowly. The smaller the piece and the higher the humidity the faster it will darken. Very small pieces may completely rust away into powder while a big chunk can remain at least partially lustrous for many years. Even the briefest exposure to air can doom the surface to some tarnishing even if immediately placed in argon. Somewhat perplexingly, this tarnishing may not be evident for days or weeks which may lead one to suspect a leak. The damage was there all along, it just took a while for it to manifest at a macroscopic level. Because of this you may notice some unevenness in the luster of your ampuled specimen. The good news is that by the time you have received it it has already fully stabilized and will retain its remaining luster indefinitely… assuming, naturally, that the integrity of the glass is not compromised.