Terbium (Tb)
Terbium (Tb)
Discovered in 1843, terbium is a rare earth metal. It’s found in cerite, gadolinite, and other minerals, and can be recovered from monazite, xenotime, and euxenite.
Terbium has a silver-gray color and is both malleable and ductile. It's actually soft enough to cut with a knife and fairly stable in air. With that in mind, it can oxidize and will become a chocolate or dark maroon color. This element has 21 known isotopes.
Sodium terbium borate is used in solid-state devices. It also acts as a crystal stabilizer in fuel cells that operate at high temperatures.