(Gr. thallos, a green shoot or twig) Thallium was discovered spectroscopically in 1861by Crookes. The element was named after the beautiful green spectral line, whichidentified the element. The metal was isolated both by Crookes and Lamy in 1862 about thesame time.

Thallium occurs in crooksite, lorandite, and hutchinsonite. It is also present inpyrites and is recovered from the roasting of this ore in connection with the productionof sulfuric acid. It is also obtained from the smelting of lead and zinc ores. Extractionis somewhat complex and depends on the source of the thallium. Manganese nodules, found onthe ocean floor, contain thallium.