Chapter 38: Dumbledore: I'm Watching You
"As you can see," said Professor McGonagall, "when one's understanding of a material's internal structural rules is sufficiently deep, when the magic is powerful enough and the intent clear enough, such a transformation can be achieved.
But as you observed, it is far more demanding than ordinary Transfiguration, because the caster must not only envision the target form — they must comprehend and reconstruct its internal stable structure, converting loose, layered connections into a rigid three-dimensional lattice."
Regulus posed a timely question: "Professor — what about the Philosopher's Stone?"
She put her wand away and looked at him. "As for the Philosopher's Stone... that represents the supreme achievement of alchemy, transcending the domain of ordinary Transfiguration.
It touches the realms of creation and eternity.
Gold produced by normal Transfiguration invariably carries a strong imprint of the caster's magic. It is unstable — prone to reverting over time or under magical interference — and possesses something fundamentally false in its nature.
Gold transmuted by the Philosopher's Stone, however, is said to possess truly permanent material properties.
The difference, perhaps, lies in whether one has actually created — or fixed — the perfect internal structural blueprint that belongs to gold."
The discussion proved immensely fruitful for Regulus.