A cumdach (Old Irish pronunciation: [ˈkuβ̃d̪ax], in Irish "cover") or book shrine is an elaborate ornamented metal reliquary box or case used to hold Early Medieval Irish manuscripts or relics. They are typically later than the book they contain, often by several centuries. In most surviving examples, the book comes from the peak age of Irish monasticism before 800, and the extant cumdachs date from after 1000, although it is clear the form dates from considerably earlier. The majority are of Irish origin, with most surviving examples held by the National Museum of Ireland (NMI).
The usual form is a design based on a cross on the main face, with the use of large gems of rock crystal or other semi-precious stones, leaving the spaces between the arms of the cross for more varied decoration. Several were carried on a metal chain or leather cord, often worn off the belt, or suspended around the neck, placing them next to the heart and thus offering spiritual and perhaps medical benefits (the same was done with the St Cuthbert Gospel in a leather bag in medieval Durham). They were also used to bring healing to the sick or dying, or more formally, as witness contracts. Many had hereditary laykeepers from among the chiefly families who had formed links with monasteries.
