When used in conjunction with bob's ores, the secondary results of mining some resources (for example, diamonds left over from mining coal) just spill on the ground. They also get picked up by belts and clog up my factory.

I saw in another thread that you can use another depot set to the secondary resources to pick those up, but a) that didn't work because the drones just started mining coal and leaving the coal on the ground and keeping the diamonds, and b) the waste products will still get picked up by belts in the mean time.

Is there any nice way to deal with this?

Great work on the mod, by the way, I really like it.

no final solution but only a small reminder since i myself often don't think of the most simple methods for (partial) solutions like "how to easily clean belts" ... in this case, a single splitter with proper filter can clean the belt and put the "trash" on another belt (optionally allowing an inserter to move all items from that splitoff belt to a chest).

a second method for cleaning belts would be a small setup with a constant combinator, a filter inserter and 1 or 2 wires that block the belt until all "bad items" are removed by the filter inserter, on another belt or directly into some chest or even void chest (this was the method to clean belts before splitters got their filters, and still has the advantage to allow more than one item type to be filtered without a chain of splitters).

of course, the problems of having secondary results not handled at all by a depot, and having to somehow collect that "trash" (cover the entire ore field with belts ? :-) still remain.

Same issue with Dyworld. Playing it at the moment and sand from the stone patches, sulfur from coal patches, acorns and carrots from trees and sand and obsidian from rocks stays on the ground, which in time start to get a server really laggy. Dyworld has an internal script which marks all items on the ground for deconstruction but we are far from robots that would do that work normally.

You could use the pickup towers mod, and put filters on any belts running through the ore patches