The ignorance in the Middle Ages of the art of gem-engraving often induced the belief that engraved stones were the work of nature. A striking instance of this was the celebrated stone over the figure of the Mother of Jesus, on the tomb of St. Elizabeth of Marburg. On this gem appeared two heads touching each other, and it was, according to tradition, not a work of art, but a freak of the sculptress Nature. An oft-repeated legend tells us that a former Elector of Mainz offered the whole district of Amöneberg for this costly stone, which robber hands removed at Cassel. It is in reality a fine onyx engraved with the heads of Castor and Pollux.[403] We might be disposed to regard rather sceptically the tales regarding wonderful stones bearing the image of Christ, or that of the Virgin Mary, and we may be inclined to believe that the old accounts are exaggerated or distorted by the pious imaginations of the writers. Nevertheless, in our own time we have a well-attested case of the discovery of such a stone. In 1880, while visiting the village of Oberammergau, Bavaria, to witness the Passion Play, Mrs. Eugenia Jones-Bacon, of Atlanta, Georgia, found on Mount Kopfel, which overlooks the village, a small stone composed of chert and limestone, and having on its surface excrescences so disposed that, when the stone was held at a certain angle, the shadows cast by them formed a striking likeness of the head of Christ as depicted in Christian art. This peculiar freak specimen has been carefully examined by experts and has been pronounced to be entirely a work of nature. The mineralogist is not disposed to see here anything more than coincidence, and yet the most sceptical cannot fail to be impressed by the fact that such a stone was found at the time and place of the Passion Play. As Max Müller said, in commenting on this strange discovery: “The chapter of accidents is much larger than we imagine,” and the present writer feels disposed to add that it is remarkable how often we find what we are looking for, especially if we are only looking or thinking of one object or subject. The religious symbolism of the diamond was a favorite theme with the thirteenth century “lapidaria,” or rhymed treatises on precious stones. Just as it could only be discovered by night—an old fancy—so was the Incarnation a hidden mystery; it gave forth a great light, just as Jesus illumined the depths of Hades when he descended thither; it was unconquerably hard, and who can resist the might of God?[404] The mediæval Italians who were fond of seeking some hidden and significant meaning in the names of precious stones, in the case of the diamond (diamante), read the phrase _amante di Dio_, or “lover of God.”[405] This was a reason for regarding the brilliant gem as a sacred stone and one especially suitable for religious use.