How do miners know when a mine is tapped out ? Or how they know where to mine in the first place?
In: Earth Science
I’m not sure about the first one, but for the second, a lot of what you do in looking for a good mine site is look at what kind of rocks and geological features are present. If you wanted to mine silver, you’d probably find a region known for it and then start looking for the types of rock which can hold large amounts of silver ore. If you’re looking for gold, you might follow the topography to find ancient river systems that would have deposited it in their beds.
You drill holes, and pull back the cores and sample and assay them. Then you draw a map with what you learned and drill more holes, map its etc. once you have it mapped sufficiently for a cost benefit to work you start digging and actually mining.
You want to know the mine is running out before you’ve done the blasting and mucking and hauling and milling if the grade is too poor to pay for the effort.
many minerals form in strips or clusters. they move on to another area with similar geologic history/characteristics when the cluster/strip has been exhausted.
> **when a mine is tapped out ?**
they rarely know it that specifically but when they can’t bring out enough valuable ore/cost they lose interest fast. there might still be good stuff down there and there might be nothing so you keep going until you start to lose profit and then you bail.
I worked at a pit mine for several years. We had core samples from the whole site. This means that before the mine was opened, the made a grid over the site where the pit would eventually be dug. Diamond drills were set up at the grid points and drilled down to the eventual maximum depth of the pit. The drill bits leave the middle portion of the material they drill around which is brought back to the surface (these are the cores). The cores are then placed on tables so you can basically see a snapshot of the minerals at every elevation level of the hole.
So once you have cores in the grid you can generate a map of where the ore (and the other material is).
This question brought up a new one for me, not sure if anyone can answer it but will there be a time when we begin to run out of things like gold and silver? Similarly to the debate on running out of natural resources like oil.
A family legend is my grandfather, a geologist and prospector, staked a claim on a copper seam that played out very quickly. A similar claim by someone else on the other side of the mountain turned into one of the largest copper mines ever.
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