During pressure oxidation of refractory sulphidic gold ores which also contain small amounts of silver, most of the silver is incorporated in the jarosite formed in the autoclave. This silver is not recovered during cyanidation and lost to the tailings. At this moment, only decomposition of the jarosite by treatment with hot lime will allow the recovery of the silver. This is a costly, often uneconomical, and messy operation, which tends to make the residue unsuitable for filtration as the jarosite reacts to a gelatinous precipitate consisting of hydrated iron oxide hydroxide (FeO(xy)(OH)ny.H2O) and gypsum.