Carl Axel Arrhenius

Carl Axel Arrhenius (29 March 1757 – 20 November 1824) was a Swedish military officer, amateur geologist, and chemist. He is best known for his discovery of the mineral ytterbite (later called gadolinite) in 1787.

The discovery of ytterbite was the first step in identifying an entire group of previously unknown elements, the rare earths. Eight stable rare earth elements were eventually extracted from ytterbite: terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium.