arsenian

Century Dictionary and Cyclopedia

1. n. One of a party in the Greek Church, in the thirteenth century, named from its leader Arsenius, patriarch of Constantinople, who excommunicated the emperor Michael Palæologus for putting out the eyes of John Lascaris, a minor and heir to the throne. The banishment of Arsenius, the appointment of a new patriarch, and the conforming of the emperor to the Latin Church at the second council of Lyons gave rise to a schism between the patriarchates of Constantinople and Alexandria which continued more than half a century.

Wiktionary

1. adj. mineralogy Describing minerals that contain pentavalent arsenic