A rare mineral found in deposits of bismuth- and arsenic-bearing minerals and typically occurring as yellowish or green botryoidal aggregates.
Atelestite is an arsenate of bismuth, Bi₈(AsO₄)₃(OH)₅O₅. Crystal system: monoclinic.
Mid 19th century; earliest use found in James Dana (1813–1895), geologist, zoologist, and teacher. From German Atelestit from ancient Greek ἀτέλεστος without end, unaccomplished (from ἀ- + τελεῖν to finish, complete + -τος, suffix forming adjectives) + German -it, with remodelling of the ending after -ite; perhaps so called with allusion to the unknown composition of the mineral when it was first described.