The village of Ytterby, Sweden is on the island of Resarö which is part of the Stockholm archipelago. It is immortalized on the periodic table. Yttrium (#39), Terbium (#65), Erbium (#68), and Ytterbium (#70) are all named for Ytterby. A centuries-old local quartz and feldspar mine produced an unusual black rock that was later found to be the source of the four eponymous elements. Four more elements—Scandium (#21), Gadolinium (#64), Holmium (#67), and Thulium (#69)—were also discovered there.

Here’s a map:

Erbium makes a Er³⁺ ion that is pink-colored and used in certain lasers. The lasers have applications in dental surgery and in optical communications. Erbium is also used in nickel and vanadium alloys and in control rods for nuclear reactors. Erbium is one of the so-called “rare earths” or lanthanoid elements.

My next post will be element #57, Lanthanum, which lends its name to the entire group!