Mineralized rock in which much of the gold is encapsulated in sulphides or other minerals and is not readily amenable to dissolution by cyanide solutions (unlike oxidized ore) even with fine grinding.

Any ore that does not respond to conventional mineral processing (cyanidation) to produce acceptable product recoveries without an intermediate step to adress its refractory attributes (usually some form of oxidation).

It is ore from which extraction of valuable constituents is very difficult. It may require special treatments, like pressure leaching, to extract the valuable minerals.