Early  days  doing   exploration  PT’d  follow the  veins   uphill by  going  from old work pit  to pit and select  surface  rocks  random, take  them back to the  placer site  and  crush them. Then he’d  pan out  gold confirming decent grades  anywhere near   a  surface  vein. Lots   of  samples comes  up with the .45 to 5.5 oz levels  to mill   vein ore  with highest  grade  from  the  hoist  shaft . Core  drills  confirmed  it  goes  deep but  turned up silver  content  not  seen at surface or  even much mined by  family for  added  value. Reason  being   silver  corrodes  and erodes and  gold  doesn’t.  Below  surface  it  hangs in   and  impure  form even more. Same  reason there are no silver nuggets  in  placer washes from near surface  stock zone.  More  recent  drilled out  shear  zone will no doubt  contain silver  as  well as  gold.   Long  as  is  there  you  take it  out as value worth the  extra  effort  to refine.   Best  is  very  low  sulfides and   next  to no base metals so working  with near  pure  free  gold stuff  to mill  and  oxidized silver, fine  gold  for  cyanide  release.

Next lighter heavy metals  are  magnetite and  hematite  which are  Iron oxides separated  by  some  magnet in process.  Panning placer  gives  black sand containing  the fine gold, a  simple  magnet picks  up all there. Rare  earth magnets  can do those and  slight  iron oxide  film can coat  gold  so various   slight  acids  remove  that. Vinegar  works but  usually  dilute  sulfuric acid .  Very fine  gold  actually floats  due  to surface  tension.  You can use  an electromagnet  as a  filter  of  built  up black sand  whiskers  to catch it  and  simply  turn it off  so the  iron floats  on  away leaving  the  very  fine  gold settled. But probably  now  will not use  a placer  process  for economy  of  scale.  Some  form of  large  gold  capture  may be  factored  in the  crush and  grind for  the  heap.  Not  sure how that would  work getting  to pebble  or  small rock size .  Milling  all gets down to a  slurry   for  table  recovery  anyway .