The main raw materials of Taoist external alchemy 道教外丹术的主要原料

The raw materials used in the refining of external elixirs are diverse. According to relevant alchemical records, there are as many as sixty to seventy kinds of mineral drugs alone. The main ones, in addition to cinnabar, include realgar, orpiment, sulfur, azurite, mica, nitre, and rong salt (a type of salt), collectively known as the "Eight Stones". Among them, cinnabar (i.e., vermilion, also known as mercury sulfide) and mercury (i.e., quicksilver) are important raw materials for alchemy.

According to historical records, as far back as the Warring States period, there were people among the common folk who became wealthy by mining cinnabar. The Shennong Bencaojing (Shennong's Classic of Materia Medica), compiled in the Western Han Dynasty, listed cinnabar as a top-grade medicine because it can be transformed into mercury (decomposed to produce quicksilver); it listed mercury as a middle-grade medicine, stating that it can "melt and revert to cinnabar" (can be reduced to mercury sulfide).