Albertus Magnus and De mineralibus: stones between science and virtue
Albertus Magnus's De mineralibus: the alphabetical lapidary, the theory of virtues, visits to mines and the spurious books of secrets attributed to him.
In the thirteenth century the study of stones took an important step forward thanks to a Dominican friar who sought to reconcile Aristotle's philosophy with the tradition of the lapidaries. Albertus Magnus, born at Lauingen in Swabia around 1200 and died in Cologne in 1280, was a theologian, philosopher and naturalist, and the teacher of Thomas Aquinas. His De mineralibus, in five books, is one of the most ambitious medieval treatises on the mineral world.
A curious Dominican
Albertus taught in Paris and Cologne, was prior provincial of the Dominican order in Germany and, from 1260 to 1262, bishop of Regensburg. He travelled widely, often on foot as the rule required, and in his writings he tells of visiting mines and questioning miners and craftsmen about their methods of working metals. He was canonised and proclaimed a Doctor of the Church in 1931.
De mineralibus was probably written around the middle of the thirteenth century, as part of the vast project of commenting on and completing Aristotle's works on nature. Since a complete Aristotelian treatise on minerals had not reached him, only excerpts, Albertus decided to write his own, combining ancient sources, Arab authors and personal observations gathered on his travels.
The alphabetical lapidary
The second book contains an alphabetical lapidary describing about a hundred stones. For each one Albertus gives its appearance, origin and traditional virtues, often citing Evax, Dioscorides and Avicenna. The virtues are explained by the theory of substantial form and celestial influence: according to this doctrine, the stars, at the moment the stone was formed, would imprint particular qualities upon it.
Albertus distinguishes with some care between what he has seen and what he reports from hearsay. In some passages he recounts personal experiences, such as the observation of gems bearing natural figures or of fossils, and shows a wish to check the claims handed down to him, while still reporting the current beliefs of his time with respect.
Seals and false Alberts
A whole section is devoted to the seals of stones, that is, the images engraved on ancient gems, which medieval lapidaries considered bearers of power. Albertus discusses their nature and interpretations, interested above all in the philosophical question of whether and how an engraved figure could add anything to the natural virtue of the stone.
The prestige of his name encouraged the circulation of spurious works. The so-called Liber aggregationis, also known as the book of secrets of Albertus, attributes wondrous virtues to stones and herbs, but it is not his work: it was written by later authors who exploited his fame. This confusion helped create the legendary image of Albertus the magician, absent from his authentic writings.
De mineralibus marks a moment when the tradition of the lapidaries met natural philosophy. Albertus does not deny the virtues of stones, but tries to explain them with the categories of the knowledge of his time and to separate observation from storytelling. For this very reason his treatise is a precious source: it shows how a great medieval intellectual looked at beliefs about protective gems with curiosity and critical sense.