Which tiny Swedish village on the island of Resaro gave the periodic table four different elements?

Ytterby is a village on the Swedish island of Resaro under Vaxholm Municipality in Stockholm archipelago (SA). The SA is the largest archipelago in Sweden and the second-largest in the Baltic sea. In 1974, the Finnish chemist Johan Gandolin analysed an unidentified black mineral found in the mine of Ytterby. He realized that the mineral was comprised of 38% new earth elements. Later Swedish chemist Andres Gustaf Ekeberg confirmed the discovery. This was proved to be the source of 4 new elements in the mineral gadolite. The elements are Yttrium (Y), erbium ( Er), terbium (Tb), and Ytterbium (Yb). These were first described in 1794, 1842, 1842, and 1878 respectively. In addition, 3 other lanthanides holmium (Ho), thulium (Tm) and gadolinium (Gd) were traced.

In 1989, the International Society ASM installed a plaque at the former entrance to the mine of Ytterby, commemorating the mine as a historic landmark. In nuclear industry, gadolinium is used as neutron absorber with isotopes 155Gd and 157Gd. Gadolinium-based compounds have medical use.