Hi Ben, theres a new gadget out called HOLY MOLY DIRT DIGGER or there abouts its hand driven but utilizes a vacum for escavation.
It sinks holes up to 14 foot only problem would be large stones id say. Have a look
Penny weight
As you can see dowels on either end entrap a smaller board tight against the wall. In return the smallar board entraps the bigger board. Hardwood is a must
There is a reason professional miners and serious prospectors use miners its the best gold trap. Cells have a tendancy to block up with pyrites and garnets plus your limited to the amount of material able to be fed threw.