I think gold cyanidation considerably reduced costs for gold extraction compared to traditional mining methods which depended on higher-quality deposits.
By "Traditional methods" I guess you mean pre 1887 methods?
You still need a relatively high (ie greater than mean crustal compisition) gold percentage to make circuit leeching (by whatever method) profitable.
On the matter of the articles discussion of uranium in the ocean - that's a dream of chasing something evermore expensive.
If there was an empty ocean basin the size of the Earths oceans and if there was an efficient cheap extraction method,
then we could pass the entire ocean through that process from our ocean to the empty basin (okay, this already sounds impractical).
Instead (if we had this hypothetical cheap extraction) we'd find ourselves endlessly pumping the same ocean through the same process and forever chasing smaller and smaller concentrations.
Your statement was "The entire history of mineral and energy extraction tells us that once dense deposits are exhausted extraction costs substantally increase even in the face of more sophisticated technology."
That statement should be independent of time, so hold for 1887 too.
> that's a dream of chasing something evermore expensive
Early gold mining (and tin, lead, etc) followed rich veins with good rewards for hand tools.
Throughout history gold mining has had bursts of finding new rich grounds, but the essential trajectory has been more effort (in the sense of moving more material) to extract less target material, often with more complex processing and harmful side effects (leaching trace amounts from paydirt).
Years back I did the computational backend for a mine modelling program (under ground and pit) with application here at the superpit [1].
The dimensions of this hole are .. large - the volume of material removed is large, and the energy requirements to lift that volume free and the sort it for discard, crushing, refining, etc are also large.
This is just for gold, which is mostly useless (aside from some jewellery and some actual essential use in space electronics the bulk of gold goes to bullion and is valuable because, well, it's gold (go figure)).
You can (I have, and others do) plot the per tonne increased extraction costs of target materials against deposit richness as reserves are depleted.
The entire notion of peak oil is predicated against increasing effort for diminished returns.
I'm far from knowledgeable about the topic. Still, I'm twinging on your earlier use of the "costs", which is different than "good rewards".
If something is rare, people may pay a lot for it. Labor-intensive manual mining (and we mustn't forget the use of slave labor hides the economic costs and adds a human cost) might not move as much material, but may still have high costs.
> plot the per tonne increased extraction costs of target materials against deposit richness as reserves are depleted.
I do understand that. But what does 'dense deposit' mean?
I took it to mean gold deposits where manual mining provided good rewards. Gold cyanidation is for low-grade ore, says Wikipedia, and the result gave good rewards for South African mine owners, yes?
What I don't know is the cost per unit production of either method.
I fully understand that new methods may make previously low-grade material economically profitable, but I don't think those should be re-categorized as "dense".
In looking around, I believe iodine production might be another case to consider. As I understand it, the historical production was from sea water through bioaccumulation in kelp, which was then dried and processed.
We've since moved to richer sources, either mineral (caliche) or brine.
"Dense deposit" means there's a lot of gold per tonne of not gold.
Manual mining produces good rewards in nugget rich grounds with dense primary rewards, if you move (say) 10,000 tonnes of material you find a lot of gold, even without extra processing (such as gold cyanidation).
When you hit low grade regions there simply isn't as much gold present - not only do you still need to move 10,000 tonnes of material, you know also need to chemically bind and extract in order to get less gold overall.
The pattern is, the easy is cheap (in terms of effort), the harder stuff costs more (in terms of effort), and minor advances in technique aside .. everything ladders upwards to cost more in extraction effort for less return.
It's been true for gold, for copper, for fossil fuels, etc.
Historically you can see hard data for this in something like [1] which is sadly a subscription service.
I interpret this as meaning that with the technology of the 1880s it was not considered a dense deposit, and earlier dense deposits were being exhausted.
This is tied back to your original statement "once dense deposits are exhausted extraction costs substantally increase even in the face of more sophisticated technology."
If it wasn't a dense deposit, then did the costs substantially increase with cyanidation? (Not total cost, but cost per unit production.)
Oh, and as a really edge case, argon gases is a renewable resource which is extracted from the air. It's cost has almost certainly gone down over time as we have improved methods for refrigeration.
You still need a relatively high (ie greater than mean crustal compisition) gold percentage to make circuit leeching (by whatever method) profitable.
On the matter of the articles discussion of uranium in the ocean - that's a dream of chasing something evermore expensive.
If there was an empty ocean basin the size of the Earths oceans and if there was an efficient cheap extraction method,
then we could pass the entire ocean through that process from our ocean to the empty basin (okay, this already sounds impractical).
Instead (if we had this hypothetical cheap extraction) we'd find ourselves endlessly pumping the same ocean through the same process and forever chasing smaller and smaller concentrations.