Hey mate need a little info on your setup you definitely should be losing black sand its not the heaviest mineral so it will migrate through the system as it should.
As for losing gold depending on your losses vs capture rate vs feedrates and throughput bit hard to know what the problem could be with no info.
Firstly do you have 3/4 of an inch of water over the cells at all Times? If not the cells dont clear out efficiently which means they are holding too much material and just like any recovery system if you throw more heavies down a choked system don't expect it to function.
To make sure you have enough water setup your gear get the water over your cells start at around 8.5 to 9.5 degrees.
Shovel some material in and have a look whats going on.... you should see material dancing in the holding cells and your cell walls clear out. If they are mot clearing increase angle and or water. Repeat.
Second to water flow is good classification, dream mat will self classify but not to shale and slate as the surface area is too large and when they go down flat they are down. I use perf plate for this reason.
3rd and something alot of people struggle with is feed rates again watch how long a shovel take to clear and get a good rhythm going.
