Congregation of Our Lady of the Sacred Heart (Springfield, Ill.)

In common terminology, there are three kinds of relics of saints. First-class relics are the physical remains of a saint, usually bone. Second-class relics are items worn or used by a saint, such as clothing or books. Third-class relics are items which have been applied to a higher-class relic, such as a piece of cloth pressed against the bones of a saint.

From the guide to the Collection of relics and reliquaries, 1795-1999, (University of Dayton)