I heard a civil engineer make a claim once that the dust on the side of the road is about 300% more laden with precious metals like platinum, than random mining. I suppose this is all roads and not just American roads, though.
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Would be fascinating to imagine it being economically viable to vacuum up and reprocess it, but based on the above I’ve assumed it was worthless.
And surface roads with stop and go would have a higher density of particles in the "go" places (like beyond lights).
But if the gangs can make money doing it why wouldn't the municipalities do it?