I was looking into these specific minerals: arsenopyrite, pyrite, chalcopyrite, barite, calcite, dolomite. I investigate issues with tellurides not showing expected gold concentrations.
There is gold predicted at the site where these samples are. We tried to prove the presence of gold through aqua regia tests, but the resulting gold concentrations are low. My suspicion is that the majority of the gold resides as an inclusion in these minerals, and the aqua regia test won't be able to show that because of its inability to dissolve the host.