Trying to create an item-on-ground via surface.create_entity() crashes if the stack item has quality. E.g.,

game.surfaces[event.surface_index].create_entity({name="item-on-ground", position=event.source_position, stack={name="iron-ore", count=1, quality="uncommon"}})

results in a crash:

Error ...

Sadly, passing quality into create_entity for a resource patch doesn't seem to do anything, probably because the prototype doesn't have quality. There's also result_quality, but it's available only for crafiting machines, which apparently doesn't include mining drills.

The spoilage idea is very ...

I'm trying to create quality ore patches. So for example, if you mined from an uncommon iron ore patch, you'd always get uncommon iron ore (ignoring quality modifiers from the mining drill). But I haven't been able to find a way to make it work. The closest I've gotten is to make my own "uncommon ...