Toned Coins For Long Term Investment

I have problems with the term "natural" toning. My understanding is that the silver is tarnishing because it's reacting to the sulphur in the air. Well earth's atmosphere doesn't naturally contain any meaningful amounts of sulphur. The sulphur in the air is a byproduct of manmade industrial processes, i.e. pollution. So what's so "natural" about the toning?

Why some collectors prefer coins that have been more exposed to man made pollution than other coins rather puzzles me, especially since most collectors prefer uncirculated, i.e. mint, coins. Well silver coins come out of the Mint looking shiny white.

It's "natural" as opposed to "artificial" or "accelerated", ie toning deliberately placed on a coin to improve its appearance, rather than toning that happened simply with the passage of time.

Silver is very good at sucking sulfur out of the atmosphere. Well, it's as good as any other metal (apart from gold) in that aspect, what makes silver unique is that it reacts readily with sulfur but not with oxygen. So while copper toning is a mixture of sulfides, oxides, carbonates etc, on silver it's pure silver sulfide.

Yes, there is (or was; it's getting better) more sulfur in the air in recent centuries due to man-made activities, particularly burning certain high-sulfur fossil fuels (oil and coal). But there would still be more than enough "natural" sulfur in the air to cause silver to tarnish, eventually. Volcanoes emit sulfurous gases, and certain foodstuffs (notably eggs and garlic) are high in volatile sulfur compounds. If everybody still lived in the Stone Age, your silver coins would still tone, just maybe 3 or 4 times slower than they do now.