Johan Gadolin, a Finnish chemist, isolates yttria,…

Johan Gadolin, a Finnish chemist, isolates yttria, a new earth or metallic oxide, in 1794 from a mineral found at Ytterby, Sweden, a village rich in unusual minerals and rare earths.

The first of the rare earths to be discovered, yttria turns out to be a mixture of oxides from which, over a span of more than a century, nine elements will be separated.

These include yttrium, scandium, and the heavy rare-earth metals from terbium to lutetium.