Mineralogy in the Middle Ages

This illustration depicts how people in the 15th century viewed the study of mineralogy and the location of precious stones.  It is by Bartholomaeus Anglicus (Bartholomew the Englishman), from a work entitled On the Properties of Things.

Credits

Image online, courtesy Bibliotheque Nationale de France, identified as:

Mineralogy: precious stones

Bartholomaeus Anglicus (Bartholomew the Englishman), On the Properties of Things
(BNF, FR 136)
fol. 73
Le Mans, France - 15th Century