Cinnabar

Cinnabar occurs as a heavy, brilliant red mineral, historically mined in enormous quantity at Almaden in Spain, at Idrija in Slovenia, and at several sites in China, where it was also known and used from very early antiquity. To extract the metal, miners and metallurgists roasted crushed cinnabar ore in a furnace, where the heat drove off the mercury as vapor, which was then led through a cooling channel or condenser and collected as liquid quicksilver dripping from the far end, one of the earliest and most reliable metallurgical extractions known, requiring only heat rather than any complex chemical reduction. Ground finely without roasting, cinnabar itself served as vermilion, the intense, stable red pigment used in painting, in the red ink of Chinese imperial seals, and in cosmetics, prized for a brilliance that few other red pigments of the period could match.

Alchemically, cinnabar's dual nature, a compound that was simultaneously an ore of the volatile metal mercury and a stable, fixed red mineral, made it an important object of study within the tria prima framework, since it appeared to embody both the fixed sulfur principle and the volatile mercury principle bound together in one substance, and its transformation under fire from red solid to silver liquid was watched closely as a visible demonstration of separating those principles. Vermilion made by grinding natural cinnabar was gradually supplemented and then largely replaced by synthetic vermilion, made by directly combining mercury and sulfur, a process attested from as early as the eighth century in Chinese and later European sources.

Cinnabar is mercury(II) sulfide, HgS, an identification with no serious historical dispute, since the mineral, the pigment, and the ore are demonstrably one and the same compound whether it occurs naturally as the red crystalline mineral or is synthesized directly from mercury and sulfur. What is worth noting for accuracy is that HgS exists in two structurally distinct forms, a stable red hexagonal crystal form, the familiar cinnabar and vermilion, and a metastable black cubic form sometimes called metacinnabar, produced under different conditions of formation or synthesis; the black form is the same substance discussed under this atlas's separate entry for aethiops mineral, and the two forms, chemically identical in composition but structurally different, were both known to alchemical practitioners even though they had no crystallographic vocabulary to describe the distinction they were plainly observing.

Chinese alchemical and pharmaceutical texts, working with cinnabar independently of the European and Islamic traditions, developed their own detailed accounts of its properties and its transformation into mercury remarkably early, a genuinely parallel line of practical chemistry worth noting alongside the more commonly cited Mediterranean sources. The clean and early metallurgical extraction of quicksilver from cinnabar by simple roasting, requiring no acid or complex reagent, made cinnabar one of the most economically important minerals of the pre-modern world wherever it was found in workable quantity.