Ann: Major extension of sulphide mineralisation at Hemi, page-113

Refractory (in gold recovery terms, not as a general definition) means basically that cyanide cant dissolve the gold grains because they are tied up chemically or covered over by sulphides (sometimes enclosed in stable oxides like haematite). Roasting or some other form of oxidation such as bacterial oxidation, autoclave, Ultra Fine Grinding with Oxygen treatment, etc... opens up the pores so to speak and lets the cyanide in. I'm no metallurgist but I think if you get less than about 80% recovery by cyanide you're in refractory territory.