Because of its organic nature and tactile qualities, ivory was sometimes associated with flesh. The luxurious binding of a gospel book, probably originally made in the eleventh or twelfth century but heavily restored in the nineteenth century, contains ivory plaques depicting the Four Evangelists (the figure of Matthew is a nineteenth-century replacement.). The ivory plaques are placed between the arms of a silver filigree cross, whose flourishing pattern suggests teeming life, a reference to the everlasting life offered to humanity through Christ's Crucifixion. That event is depicted in gold leaf at the center of the cross, protected by a large rock crystal. In this example, the materials help the viewer to interpret the conceptual structure of the work. Whereas the figures of the Evangelists, the human transmitters of the gospels, are tangible and tactile, the image of the crucified Christ has a floating, ghostly quality, mediated and refracted by the curved surface of the crystal. Rock crystal was understood as frozen water and because of its transparency was associated with purity, hence with Christ: its dual nature as liquid and solid is invoked here to suggest Christ's status as hovering between the world of the flesh ad that of the spirit.