fl. 1480s

Italian astronomer, mineralogist, and physician whose Speculum lapidum (1502) treats over 200 minerals. This compilation proceeds according to traditional knowledge and concepts, relying little on independent observation, although the invention of gunpowder is alluded to. His focus is primarily the occult powers of gems and images carved upon them. Leonardus also worked on astronomical tables, verified the positions of particular stars, and published astrological rules for bleeding and administering drugs.