On the nature of gold in hermetic texts
A short study of how "aurum vulgi" and "aurum philosophorum" were distinguished in early Latin grimoires — and why the line blurs among the late commentators.
The 13th-century Speculum alchemiae, traditionally ascribed to Roger Bacon, opens its chapter on gold with a clean split: there is gold one can buy from the money-changer, and gold that is born from an inner process. The first is aurum vulgi — market-gold; the second aurum philosophorum — philosophical gold.
Two hundred years later, in the Paracelsian treatises, the distinction begins to compress. For Paracelsus "gold" is not a material but a condition. His Archidoxis uses the term as a metaphor for the maturity of any substance: a mineral that reaches full realisation of its nature is already "gold."
By the baroque period (Fludd, Maier, Pulicius) the line is wiped away. "Gold" stands for "truth in general" — convenient for persecuted authors and inconvenient for the historian trying to reconstruct laboratory practice.
The library holds three key sources on this transformation; for a first reading we recommend beginning with the Speculum — short, clear, and still possessed of its materiality.