Ekeberg analyzed a number of the minerals found at Ytterby and Falun. In 1802 he analyzed specimens of tantalite from Kimito, Finland, and of yttrotantalite from Ytterby, Sweden. He is credited with finding the element tantalum in both.
Ekeberg named the new element after the mythical Ancient Greek demigod Tantalus. According to legend, he was condemned to eternal frustration when he had to stand in water up to his neck, but the water receded as he attempted to drink.