Tellef Dahll (10 April 1825, in Kragerø – 17 June 1893, in Morgedal) was a Norwegian mineralogist and geologist.

[1] After graduating in minearology from the University of Christiania in 1846, Dahll worked for private mining companies.

He found coal on the island of Andøya, iron ore at Bjørnevatn[2] and in 1867 Dahll discovered gold from the Tana and Anarjohka rivers, which launched the 1870 gold rush in the Finnish Lapland.

[4] In 1879 Dahll collected samples of nickel arsenide and gersdorffite on the island of Oterøya in his birthplace Kragerø.

Dahll found out that the rocks contained previously unknown element which he named Norwegium.