Ideas are like gold nuggets in a river. Constantly traveling past you, most of them without your appreciation. You may reach out and catch one or two but often they will slip from your grasp and be on their way. If you want to hunt gold nuggets for a living, you have to spread a trap for them; a net or a sieve, something that makes it harder for them to escape. But once you break their run, the work isn’t done yet. You have to evaluate them, then put them in the right place.
Unlike real gold nuggets, these metaphorical ones only have their value in the company of other nuggets. Perhaps the size of the nugget is the best metaphor: a small nugget isn’t worth much but a whole lot of them could mean something. Then there’s always a chance of stumbling over that large, huge nugget that can be valuable by itself.
Large nuggets are short story ideas, where a single idea can form a meaningful message. Smaller nuggets clump together to form a novel. One by one, they are not very appreciated but once they become gold dust they each contribute to the entire value.