Nam lucet in colore ut rubinus per animam tingentem, quam acquisivit ex virtute ignis; propter hoc ignis dicitur tinctor.
This passage establishes the ruby as the paradigmatic image of the fire-tinctured soul in alchemical Latin, where it shines by virtue of the animating tincture acquired through fire—making ruby the emblem of soul-infused, fire-perfected matter.
, Aurora Consurgens: A Document Attributed to Thomas Aquinas on the Problem of Opposites in Alchemy, 1966thesis