Ann: Market Update, page-287

From the last page of the Ian Plimer article (my italics):

"The occurrence of gold substituted in sheet silicates as Au3+, will cause lower gold recovery. In the deposits studied, the amount of such gold changes from about 20% in Maldon to about 10% at Barberton. This gold will form a constant tail in the mineral dressing waste. The technology, suitable to recover gold of this type, is a matter of further research. So far gold silicates have been detected at Maldon, Australia, Barberton, South Africa, and at the Barramiya prospect, Egypt. It may be expected that in mesothermal and epithermal gold deposits these compounds may be common, and locally may affect gold recovery."