Georg Agricola’s use of “fossilium” and “metallica”: fossils, metals, minerals?

Georg Agricola wrote three books with the words “fossilium” or “metallica” in their titles: “Bermannus, sive De re metallica” (1530); “De natura fossilium” (1546); and “De re metallica” (1556). The phrase “on|of the nature of metals” is often seen as an English equivalent of “de re metallica” and the phrase “on|of the nature of fossils” is often seen as an English equivalent of “de natura fossilium”. I suspect these readings are incorrect.

I think that an appropriate rendering of Agricola’s...

Georg Agricola’s use of “fossilium” and “metallica”: fossils, metals, minerals?