According to Harran school, substances form in the first operation, as rust develops from iron.

Although this statement has been associated with Agathos Daimon, it instead seems to have its origin in the Harran school, which is based mostly on Agathos Daimon and Hermes axioms.
The first one is a legendary author, like Hermes. And, just like Hermes, he lacks evidence about his very existence shade into divinity. Agathos Daimon takes part in the Egyptian and Greek pantheon, sometimes represented as a serpent, sometimes as a boy with a cornucopia. When speaking of Harran school, we are allowed to assume a date from 4500 till 1200 b.c. due to the prevalence of copper in their writings. But what Harranian alchemists intended for copper is questionable and will be the object of a coming post.
The sentence:” Substances form in the first operation, precisely like rust develops out of iron”, should be taken as an allegory or as an actual operative sentence. Rust pops out from time to time in hermetic texts; later authors seem pretty uncertain about its usage, as though it were an ancient deep secret. Fulcanelli and Canseliet, too, puzzled themselves about.
This expression is perhaps one of the most precise and detailed about rust in the whole hermetic literature. We can try to intend Rust as iron oxide commonly. Indeed Hermes and Cleopatra have talked much about taking crude matter or materia tertia out for an airing. As suggested in varied hermetic illustrations such as in Orthelius and Mutus Liber. This process is customarily known as “ Magnetization” and concerns an enrichment in Secret Fire or Mercurius of Wises falling from the sun and the moon. We already know that atmospheric O2 is particularly rich in Secret Fire. However, we cannot understand how and why.
What does Harranian mean by “ first operation”? A previous magnetization by airing or canonical cooking inside a vessel? The whole enigma here seems to lay on Work phasing. In The Origins of Alchemy in Graeco-Roman Egypt” by Jack Lindsay, 1970, page 327, we can find: “… according to Hermes, in his Little Key, ancient alchemists by saying “ Purple or Purple Stone” used to envisage copper rust or better Copper Rust. “
Now a quotation from Timaeus by Plato may be more explicative:” In the next place, we may observe that there are different kinds of fire— flame, light that burns not, the red heat of the embers of the fire. And there are varieties of air, for example, the pure aether, the opaque mist, and other nameless forms. Water, again, is of two kinds, liquid and fusible. The liquid is composed of small and unequal particles, the fusible of large and uniform particles, and is more solid, but melts at the approach of fire and then spreads upon the earth. When the substance cools, the fire passes into the air, which is displaced, and forces together and condenses the liquid mass. This process is called cooling and congealment (solidification and coagulation). Of the fusible kinds, the fairest and heaviest is gold, hardened by filtration through rock and is bright yellow. A shoot of gold darker and denser than the rest is called adamant. Another kind is copper, which is harder yet lighter because the interstices are larger than in gold. There is mingled with it a fine and small portion of the earth which comes out in rust. These are a few of the conjectures which philosophy forms, when, leaving the eternal nature, she turns for innocent recreation to consider the truths of generation.” Key words here are coagula, earth, and rust. Or give a body to whatever is free of the body.

Harran school is closely associated with minerals and metals usage. But pay attention to what Adfar, better known as Stephanos of Alexandria, many centuries after Harran ceased to exist, has to say about metals and their calcination or reduction to powder:” You don’t have to be afraid of calcinating all these bodies, for they are brought down into Spirits and regain their native power. In so doing, they get an ability to copy the universe; thus, employing a material spirit, they come to be born again.” Reducing rust may be equivalent to reducing to powder, an operation better known as Calcination. A process that can have something to do with the coagula phase. But we know that there are coagula phases in every work.
So there is calcination in the Labors of Hercules, the very first operation, and calcination in the Main Work, just the first operation. In the labors of Hercules, in so doing, we dissolve and break Materia Tertia, while in the Main Work, we recompose Materia Prima. ( see an Opus Magnum scheme) .