Looking at the earlier announcements it appears the first mining area was MB3, which had a resource estimated sieved Rx silica of 4.6%, which was the highest Rx silica at Bald Hill, and the 24/3/15 and 19/3/15 announcements talk a bit about the results to date and reconciliation which was described as 'fair to good'. So 5% Rx doesn't look unreasonable for the port stocks assuming the whole production came from that area, and on that basis shouldn't be reflective of the whole thing.
