Amalgam forms readily when mercury is brought into contact with finely divided gold, silver, tin or several other metals, the mercury dissolving the metal's surface and combining with it to form a soft, pliable, silvery alloy without requiring any furnace heat, a genuinely striking property among alchemical transformations for how easily and how visibly it happened at ordinary room temperature. The most economically and artistically important application was fire gilding: a paste of gold amalgam was spread evenly over the surface of a base metal object, typically bronze or silver, and the whole piece was then heated, driving off the mercury as vapor and leaving behind a thin, tightly bonded layer of pure gold fused to the object's surface, a technique used across the ancient, medieval and early modern worlds to gild everything from small jewelry to large architectural and religious objects, though the process released substantial toxic mercury vapor with essentially no protection for the artisans performing it, a serious, well documented occupational hazard of the gilding trade.
Amalgamation was also used, alongside roasting cinnabar directly, in refining silver and gold from low grade ore, since finely crushed ore mixed with mercury allows the precious metal to be selectively extracted into the amalgam and then separated from the mercury by heating, a technique deployed at enormous industrial scale in Spanish colonial silver mining in the Americas from the sixteenth century onward, with correspondingly enormous and well documented human and environmental costs from mercury exposure.