The Green Lion is one of the most celebrated and debated symbols in the entire alchemical canon. Unlike the red lion (representing mature, fixed sulphur) or the paired winged and wingless lions of the mercury-sulphur theory, the Green Lion is a substance in its own right: the raw, unripened ore from which the work begins. The colour green signals immaturity and potential, like unripe fruit on the branch, and also connects to the verdigris of copper, a substance linked to the leprosy of metals that must be washed away for regeneration to occur. The Green Lion occupies the liminal space between base matter and philosophical gold: it is the prima materia at its most promising and most dangerous.

In alchemical tradition, the Green Lion has been variously identified as raw antimony ore, green vitriol, the unclean body of the prima materia, and philosophical mercury in its earliest stage. Abraham explains that according to most alchemical texts, the Green Lion is the ore from which philosophical mercury is extracted, also known as terra (earth), the unclean body, or Latona. St Dunstan wrote that three things are chiefly spoken of the Green Lion, Assafoetida (the stinking odour exhaled from the unclean body), and white fume (the white smoke that arises before the red tincture ascends). Two crucial spirits are extracted from the lion ore: one is the red, stinking blood of the Green Lion, which can dissolve and reduce all metals to their first matter. When alchemists speak of the Green Lion devouring metals, they mean this mercurial blood dissolving everything it touches. Some alchemists identified the Green Lion as vitriol, but Ripley disagreed, calling vitriol what fools call the Green Lion.

Maier addresses the Green Lion most directly in Emblem XXXVII of the Atalanta Fugiens, whose motto derives from Morienus' De Transmutatione Metallorum and names the three pillars of the masterpiece: stinking water, the Green Lion, and white smoke. The epigram declares that three things form the foundation of the mastership: stinking water, snow-white vapour, and a lion with a green fur, and that the ore of Hermes is the Green Lion. The discourse develops these three substances at length, explaining that the stinking water is the initial stage of the process, the Green Lion is the middle stage, and the white smoke is the final result. Maier also refers to the Green Lion in Emblem XXVIII, where king Duenech shines with the weapons of the Green Lion, connecting it to the allegory of the sick king whose purification involves the strongly caustic, dissolving power of green vitriol.

De Jong identifies the Green Lion as green vitriol, which has a strongly caustic, dissolving effect, and notes that Emblem XXVIII speaks of the Green Lion in the allegorical form of king Duenech. She traces the motto of Emblem XXXVII to Morienus and the commentary of the Consilium Conjugii, which explicates the three kinds as the white smoke (the quintessentia or heavenly water), the Green Lion (the ore of Hermes), and the stinking water (the mother of all things, from which and by which and with which the Stone is prepared at beginning and end). De Jong clarifies that the stinking water represents the initial stage, the Green Lion the middle stage, and the white smoke the final result, and that the Rosarium describes the Green Lion as possessing a blessed green colour that produces all other things, a sign not of impurity but of perfection.

The Green Lion is arguably the most vivid example of Maier's method of concealing chemical instruction within arresting imagery. The reader encounters a lion with green fur, an impossible creature, and must puzzle out that it represents a caustic mineral substance whose dissolving power is the engine of the entire alchemical process. The blessed greenness that the Rosarium praises is the colour of growth, of spring, of the seed from which living gold may be grown. Maier's lusus serius asks the reader to see in this fantastical beast not a fairy tale but a precise description of a chemical reagent, one that the wise alchemist must identify, obtain, and deploy with care, for the Green Lion devours everything it meets.

Meanings Across Registers

De Jong shows that alchemical terms operate simultaneously across material, medical, spiritual, and cosmological dimensions.

Alchemical

The vitriolic mineral acid (often green vitriol or its derivatives) figured as a green lion that 'devours the sun': the corrosive solvent that dissolves gold to begin the work.

Medical

The aggressive purgative whose corrosive virtue scours obstructed humors from the body; the violent remedy whose green color signals its derivation from copper-bearing minerals.

Spiritual

The hungry, untamed vitality of the unintegrated psyche; the wild green of unprocessed life-force that consumes the sun-king of consciousness before it can be tempered.

Cosmological

Venus and Mars commixed: the copper-iron complex whose vegetal green marks the earth's productive force, the chthonic appetite at the root of all generation.