Gold in Quartz - February 2016 (Vol. 85, No. 06) - ICMJ's ...
Crushing the ore can free the gold and allow recovery by gravity-based methods. In fact it's very common that the gold in hard rock ores will range in the 30- to 200-mesh size range with most of the gold in the lower end of that range. The tried and true method for testing these ores in the field is hand crushing and panning.