Ann: Gold Extraction Results from Ema and Tres Estados, page-214

Ores with gold that is difficult to extract is not that rare. just google refractory gold ore. All kinds of metallurgical reasons why when gold is association in compound form with other elements the ore does not respond to normal extraction techniques such as cyanidation. Different ores require different pre-treatments to render the gold into a form that more conventional leaching or pyrometallurgical processes can then bring about the extraction. One unique feature to all these ore types is the gold is in incredibly fine form, often surrounded with a sulphide coating or other species. I have no issues with the BBX discovery. The drilling will tell all eventually.