Walk around and pick up a random rock. On average it’s 5% iron which combined with just a little carbon makes steel, so no we aren’t running out.
This is also why the Iron Age was such a big deal. The bronze age required both copper and tin which where rare and didn’t generally show up near each other while you could operate a shitty iron mine just about anywhere.
Not that we would necessarily run out, but would a 5% ore be financially viable, and how many places would be able to operate it (geology for underground mines, location/eco concerns for strip mines)? We also have to question they typical coke and smelting process.
Economic viability is largely a question of competition between alternatives. As long as 60% iron ore is available there is little reason to focus on 30% iron ore and so on. Today 60% iron ore is only worth about 100$/ton.
Hypothetically, if we where down to 5% being the best option, then chances are your backyard would be just as viable as anywhere else. Plants will happily grow grow with up to about 55% iron in their soil. So in some place you could literally just use surface dirt as your “ore.”
Because anyone who chucks a (copper-based) rock into a standard wood fire will notice the copper that melts out of the rock. Tin's melting point is only 500F for example (one of the components of Bronze), while Iron's melting point is ~3000F.
It has to be the _correct_ rock, but chucking random things into a fire is an activity that all humans like to do. Its only a matter of time before some human chucks the right rock into a wood fire to discover Tin and begins the Bronze Age.
Iron however, is far more difficult to process. One theory is that early Iron-age was helped by meteors, as pure-iron rocks from the sky would be objects of worship to any human. After experimentation with the space-metal, they'd discover the incredible properties of iron.
With the "Seed of knowledge" planted in the human's brains from space rocks, humans would build hotter fires that can better process the space-rock / space-iron (maybe not reaching 3000F, the melting point, but maybe 2500F for hot enough to make it malleable / hammerable).
Once this discovery is made, its only a matter of time before people chuck _other_ rocks into the 2500F fire and start hammering to look for the common iron that's all around us. So the process is instead to heat the iron as hot as possible with your current technology (again: maybe 2500F) Then, you smack the hot rock with a hammer until you squeeze all the impurities out (while shoving it back into the fire to keep it at 2500F+ as much as possible through this process).
Once the impurities are gone, you're left with pure iron, equivalent to the space rock.
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This iron-age process (even for the simplest of ores) is far more difficult to "discover" than "chuck the correct rock into a fire".
You really can start mass producing iron when you can melt the darn thing, which requires a blast furnace. But "Iron Age" smiths were largely with simpler forges / fires and with the "hammer method" IIRC.
Bronze is much easier to create than iron which requires higher smelting temperatures. The only reason we were able to was likely through advances smelting bronze.
AFAIK Africans, that is, the Bantu and related West African peoples, went directly from Neolithic to Iron Age, skipping Bronze.
For Mediterranean, it's mainly because the whole region, Iraq, and Northwest India/Pakistan were already integrated together as a trading unit, with factors coming hp from Sumer and Assyria to trade with Dilmun, Indus Valley, and Anatolia. Then the Phoenicians traded tin from Iberia and all the way from Britain as well.
Funnily enough, Egypt only adopted bronze (and chariot) at least for their armies after the whole Hyksos invasion stuffs. That might be the basis for Exodus.
This is also why the Iron Age was such a big deal. The bronze age required both copper and tin which where rare and didn’t generally show up near each other while you could operate a shitty iron mine just about anywhere.