gems, early lapidaries, early gemology, early mineralogy, Leonardus, Mirror of Stones, Speculum Lapidum

In the Middle Ages, precious stones were used in a wide variety of ways. While their therapeutic and symbolic properties are well known, much less is known about their talismanic and magical virtues. Leonardi’s compilation offers us an excellent overview of these. It primarily concerns seals and stones engraved with planetary, zodiacal, and decanic figures, or with magical characters. It allows us to glimpse a world of belief in which astrology plays a determining role, since gems were endowed with the power of stars and constellations through engraving—when the stone was not already engraved by nature. The traditions Leonardi transcribes are largely unfamiliar to medievalists, although they deserve to be brought out of the shadows, if only because they had a great impact from the Middle Ages to the dawn of modern times.