There appear to many stopes of high grade material taken out below what the informales would be capable on there own, whereas historical data shows us that about 35 meters was the informaly maximum depth. The C-1 has 4 of these stopes that may have been innaccessable to the informales, and the A-4 has about 3. This is looking at data though that is several years old, newer data suggests that there has been considerable work done on the deepening of these adits, and NR,s clearly show the increase in gold grades at depth. Also, a 4 ton bulk sample taken from the 42 m level, (i believe it was), averaged 11 ounces per ton! Thats 44 ounces of gold from a pile of dirt that could fit on the back of a half ton. There has also been a sample of ~5kg taken from the C-1 vein which assayed 11 ounces per ton.
These photos below can be seen larger in our photo section tab here on Agoracom to your upper left.
C-1 Underground Workings
A-4 Underground Workings