The thing with shafts, or in fact any diggings, is to get to know the legal conditions of the area they were allowed to dig. the shaft, or smaller diggings, are only an indication of the surface access to a wider underground level. take for example a deep reef mine - single (or safety double) access point, yet the mines spread out for miles both vertical and horizontal. A lot of the old mine shafts by looking down them are hard to see how far sideways they go, usually a yard or two, but have been subjected to erosion and collapse. The drives, as shown in MJBs drawing are what is happening - they hit the gold bearing wash then went as far sideways as they were allowed to (and also a bit further, hence the reports of underground 'claim jumping'.) Same for shallow diggings - they were only allowed a certain footage area to dig on their Miners rights/Licence.
The small quartz is interesting - that is the last thing out of the hole prior to hitting the wash layer by the sounds of it or maybe even the top of the wash. A small coil or a VLF should certainly give an indication of gold. Some of the gold could still be encased in what appears to be quartz or stone but is in fact super hard pipeclay - seen that a lot and the old timers missed it.
As for digging down, if they had a right to drive sideways from the shafts, which they would have, you may end up digging straight into a horizontal shaft - it happens. Dig, dig, dig, then the ground disappears beneath your feet and you may be many yards/metres from a shaft. Quite hair raising. I would most certainly concentrate on the mullock and the outside skirt of the mullock where the heavier stuff (hopefully gold) would have rolled/eroded to. Might also pay just to have a quick check of water runs off the mullock - these soils may have picked up gold. My mate Trev does these mullocks/quartz over a lot - takes buckets of the stuff and pans it for some nice little results.
The thing with mullock is - what is on top is the last thing out - always - no exception. If the ground is sloping, usually the gold bearing wash was taken out on the downhill side to prevent it falling back in and it was easier to cart away.
take a moment, have a brew, sit on a mullock heap, picture it 150 years ago, its hot, water is expensive, food is crap, you NEED to make a living, the missus is nagging you, the booze is second rate, the old boilers tempt you with their cunning ways to extract your hard-earned, the government is a pain. What is the easiest and quickest way to get this stuff out and washed - follow their lead (so to speak).
