SMARAGDO. - Benedictine writer, active in the first decades of the 9th century, perhaps of Irish origin, a monk at Castellio on the Meuse; as abbot, in 819 he transferred the abbey to S. Michele on the Meuse (diocese of Verdun).
As a monk he compiled a Liber in partibus Donati in 15 books, a grammatical commentary. He also wrote a commentary (liber comitis) on the Epistles and Gospels
of the year, for which he made use above all of Augustine, Jerome, Gregory, and Bede. He compiled, probably for Carlomagno, a Via regia as an ascetical mirror for princes, based especially on Proverbs and Wisdom. A Diadema monachorum is dedicated to the monks of S. Michele; on the occasion of the reform of the monasteries undertaken by s. Benedetto d'Aniane and by Lodovico il Pio (817), he composed a commentary on the Rule of s. Benedetto. Other minor writings are attributed to him, and it is difficult to distinguish what instead belongs to Benedetto d'Aniane. On a small work concerning the Procession of the Holy Spirit, cf. Hefele-Leclercq, III, p. 1131. The year and day of his death are unknown.