The Instructor 2.12.118

To gape at stones, dark or green, the refuse cast up by a foreign sea and the scrapings of the earth, is childish. For to rush after translucent pebbles and stones of peculiar colors and varied glass is nothing but the mark of foolish people drawn by things that strike the imagination. So children, seeing fire, rush toward it, drawn by its brightness, not understanding through folly the danger of touching it. Such are the stones that foolish women fasten on themselves in chains and necklaces: amethysts, thunderstones, jaspers, topaz, and the Milesian emerald, the most precious merchandise. And the much-prized pearl has marched in extravagantly into the women's quarters. It is formed in a kind of oyster like the pinna, and is about the size of a large fish's eye. And the wretched women are not ashamed to have spent all their zeal on this little oyster, when they could adorn themselves with the holy stone, the Word of God, whom Scripture somewhere has called a pearl, the translucent and pure Jesus, the eye that watches in the flesh, the transparent Word, through whom the flesh is made precious, regenerated by water. For that oyster too, formed in water, encloses the flesh, and from this the pearl is conceived.