the quicksilver is a material substance and at the same time a living spirit whose nature can be expressed by all manner of symbolic synonyms — though only, it is true, when it is made fire-resistant by artificial means.
Jung establishes quicksilver's defining paradox: it is simultaneously a physical substance and a numinous living spirit, accessible as symbol only through the transformative work of the alchemical art.
, Mysterium Coniunctionis: An Inquiry into the Separation and Synthesis of Psychic Opposites in Alchemy, 1955thesis