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Resolving the 'invisible' gold puzzle
Phys dot org ^ | Wednesday, May 1, 2019 | Helmholtz Association of German Research Centres

Posted on 05/01/2019 9:17:02 PM PDT by SunkenCiv

The Carlin-type gold deposits in Nevada, U.S., are the origin of five percent of the global production and 75 percent of the U.S. production of gold. In these deposits, gold does not occur in the form of nuggets or veins, but is hidden—together with arsenic—in pyrite, also known as "fool's gold." A team of scientists from the Helmholtz Centre Potsdam—German Research Centre for Geosciences GFZ has now shown experimentally, for the first time that the concentration of gold directly depends on the content of arsenic in the pyrite. The results were published in the journal Science Advances.

In the Earth's crust, the element gold occurs in concentrations of 2.5 parts per billion (ppb). In order to mine it economically, the gold concentration must be thousands of times higher and it must be found in a focused area close to the surface. In the gold deposits of the Carlin-type, the gold in the rock is not visible to the human eye. Instead, the 'invisible' gold occurs in tiny pyrite rims that grow on older fool's gold grains which originate from sedimentary rocks.

In the laboratory experiments, the researchers around Christof Kusebauch, lead author of the study showed that the element arsenic plays the crucial role in extracting gold from hot solutions probably from magmatic systems, passing through the rock. The higher the concentration of arsenic, the more frequently gold chemically binds with pyrite. The shape of the older pyrite is also important: the larger the surface area of the mineral, the more gold can accumulate.

Arsenic indicates gold deposits

Similar to the natural ore system, the authors used iron-rich carbonates and sulfur-rich solutions to synthesize their fool's gold crystals.

(Excerpt) Read more at phys.org ...


TOPICS: Business/Economy; Science
KEYWORDS: arsenic; foolsgold; gold; nevada
Natural pyrite, also called 'fool's gold', in its typical cubic crystal shape. Credit: C. Kusebauch, GFZ

Credit: C. Kusebauch, GFZ

1 posted on 05/01/2019 9:17:02 PM PDT by SunkenCiv
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To: AdmSmith; AnonymousConservative; Arthur Wildfire! March; Berosus; Bockscar; cardinal4; ColdOne; ...
I *may* be the only person on FR who found this fascinating. Probably an application to asteroid mining in there somewhere, eh? When the platinum metals were discovered and isolated, the silversmiths figured out that doping the hot metal with arsenic allowed them to sculpt or build up a work of art (solid platinum metals) by adding soft bits. The trick was, don't inhale the smoke.

2 posted on 05/01/2019 11:07:02 PM PDT by SunkenCiv (Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
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To: SunkenCiv

I’m reminded of the Friday swimming days when all the students of my class in the last year of primary school, would troop down to the river and change into a bathing suit behind the blackberry bushes...girls on one side, boys on the other, and jump into the swimming hole by the willows. There, glistening in the sunlight, the flecks of fools gold flowed by in the current and ran between our fingers.

Should we have been looking for gold somewhere upstream?


3 posted on 05/01/2019 11:54:32 PM PDT by Fred Nerks (FAIR DINKUM)
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To: Fred Nerks
Heh, it's pretty in its own right, IMHO. Somewhere around here, from my childhood, there's some kind of geological sample collection, and it includes chalcopyrite.

4 posted on 05/01/2019 11:59:03 PM PDT by SunkenCiv (Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
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To: SunkenCiv; All
The Carlin-type gold deposits in Nevada, U.S., are the origin of five percent of the global production and 75 percent of the U.S. production of gold. In these deposits, gold does not occur in the form of nuggets or veins, but is hidden—together with arsenic—in pyrite, also known as "fool's gold."

From the fantastic “How The Earth Was Made” documentary series...

They begin discussing the “Carlin Trend” at the 27:16 mark of the ~45 min doc.

Season 2, episode 13: America’s Gold
https://www.youtube.com/watch?v=6baHoiV6ltg

PS-I certainly find this interesting, having majored in geology back in my mid-1980s college days. :)

Thanks for posting!

5 posted on 05/02/2019 3:43:07 AM PDT by ETL (REAL Russia collusion! Fake Dossier, Uranium-1 Deal, Missile Defense, Iran Deal, Nukes: Click ETL)
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To: SunkenCiv

We have “Borg” pyrite all over in our rock gardens. Pretty easy to find on a day field trip from the El Rancho. BTW the gold content can vary significantly within a mine. Well run mines drill core samples and map the deposit. They operators know almost to the gram what the yield will be per ton.

The Carlin deposit is a pretty unique formation. I would be surprised to find it on an asteroid or another planet.


6 posted on 05/02/2019 3:55:04 AM PDT by mad_as_he$$
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To: SunkenCiv; mad_as_he$$; All

This site linked below has transcripts for the How The Earth Was Made documentary series.

I’ve copied (below) the portion of the episode that deals with the Carlin Trend and related-type gold deposits.


From season 2, episode 13: America’s Gold, approximately the 27:16 mark:

“Nevada’s hot-spring gold deposits yielded over 40 million ounces of gold and 500 million ounces of silver, but by 1920, Nevada’s gold seams were increasingly uneconomical to mine. The desert became littered with ghost towns. It looked like America had run out of gold.

But in 1961, a new type of deposit was found. But it couldn’t be seen or touched. It was invisible. It would become the biggest strike in the history of America’s gold.

America’s gold was concentrated by incredible mountain-building forces that formed California, and volcanic processes deep beneath Nevada’s hot springs. But as the deposits became exhausted, geologists frantically searched for new stashes of gold.

Then in 1961, geologist and gold prospector John Livermore noticed a suspicious [50-mile crack] in the middle of Nevada called the Carlin Trend and set out to investigate.

John Livermore came to these hills following up a theory that gold deposits would be aligned directly above a deep crack in the Earth’s crust. He’d come up to outcrops like this, and he would go ahead and want to look at them.

The rocks are a strange mixture of mud and quartz, a mineral created in hot fluid and a good clue that gold might be deposited nearby. Based on his experience, he knew a lot of hot fluid had come up this crack.

However, he couldn’t see any evidence of gold, no quartz veins, no visible gold.

But on a hunch, he sampled this rock, took it back to the assay lab to see if there was any gold in it.

In assay labs, rocks are crushed and blasted in a furnace to over 1,800 degrees. And as the liquid rock cools, the minerals begin to separate.

At the end of this process, something extraordinary has happened.

An ordinary-looking rock actually contained a grain of gold at a concentration of about 5,000 times you would normally see in the Earth [crust].

It doesn’t look like much, but this is what they mine every day.

Livermore’s hunch paid off. The Carlin Trend is now one of the largest mining districts in the world.

The vast man-made pit is big enough to be seen from space.

This is the BetzePpost pit, one of the world’s largest gold mines.
It contains 45 million ounces of gold. They have to mine to get one ounce out.

As you can see, it’s huge— Because gold is so valuable, the extraction of just a few thousand ounces a day pays for this extraordinary mining operation. And removing the gold ore requires drastic action.

[explosion] Wow. That’s what 400,000 pounds of explosives looks like.

Giant diggers work 24 hours a day excavating over, enough to cover Central Park in 55 feet of rubble.

But within this raw gold ore, not a speck of gold has ever been seen with the naked eye.

The mystery is, where’s the gold?

You can’t see it. The rocks look really ordinary. The clue to where this gold is hidden is in the internal structure of this rock.

Magnified 500 times, the gold is still invisible.

But this rock is an extraordinary lattice of quartz and mud perforated with strange cavities. It looks like a honeycomb, like something’s eaten away at it. Clearly some strange geologic process has concentrated and hidden the gold in the rock.

Scientists realized if they were going to solve the puzzle of how gold came to be hiding in these rocks, first they would have to understand where the rocks came from.

A clue was found in the 19th century by cattle rancher Absalom Lehman in the eastern reaches of Nevada.

In 1885, Absalom Lehman stumbled upon a hole in the ground, and with rope and lantern, he lowered himself in the Earth and discovered this beautiful cave system with some of the most spectacular [limestone] cave formations in the world.

The solid foundations of this cave are made of a messy mixture of mud and calcium carbonate shells.

They are the remains of tiny sea creatures, evidence that Nevada was once covered by an ancient tropical sea.

For millions and millions of years, creatures with shells composed of calcium carbonate began to rain down through the ocean and accumulate on the sea floor forming this calcareous ooze.

Later, this ooze hardened into a sedimentary rock called limestone.

These extraordinary structures in the cave were formed when water eroded the huge limestone bed that sits underneath Nevada.

And back over at the Carlin Trend, scientists noticed that the gold ore was made of a very similar type of rock.

They figured out that the Lehman Cave limestone and Carlin Trend gold ore must once have been the same rock.

Clearly something happened to change this rock into this spongy gold-bearing ore.

Well, the clue is in the chemical reactivity of this limestone.

If I put dilute hydrochloric acid on this limestone, note how it fizzes. Very reactive. The acid is eating away at the rock.

Now if I put the acid on the spongy gold ore, no reaction. The fluid is soaking into the rock like a sponge.

Scientists concluded the reason Carlin Trend gold ore did not fizz is that it had already been attacked by an acid.

Beneath the bed of limestone at Carlin is a gigantic vertical crack.

Geologists now believe that a blast of hot, acidic gold-rich fluid was once forced upwards from deep within the Earth.

It streamed through the crack, drenching the limestone.

The acid ate into it, leaving a sponge-like muddy framework behind.

And in the cavities, it dumped quartz and the most minute sprinklings of gold.

It’s only been very recently that scientists have been able to use even more sophisticated imaging equipment—microscopy— to image down to the scale of individual atoms.

Magnified 100,000 times, tiny specks of submicroscopic gold can be seen embedded in the rock.

Zooming in further a staggering 4 million times, the gold particle is finally revealed.

This fleck of gold is only one-millionth the size of a pinhead, and each tiny white dot is an individual gold atom.

These ordinary-looking rocks have produced 65 million ounces of gold from a single crack in the Earth known as the Carlin Trend, and it’s made the United States the fourth largest gold producer in the world.

Scientists investigating how Nevada’s gold ore formed have found a sponge-like rock structure, suggesting that something ate away at the limestone, and gold ore not reacting with acid, evidence that an acidic fluid had already attacked the limestone, showering it with minute particles of gold.

Similar Carlin-type deposits have since been discovered yielding a further [35 million ounces of gold]

Yet these discoveries may only be the tip of the iceberg.

Geologists are now using state-of-the-art equipment, hoping to unlock millions of ounces of American gold trapped deep beneath the Nevada desert.

Throughout world history, over 5 billion ounces of gold have been recovered by man, and almost 1/10th of this has been found in California and Nevada, adding up to a staggering $280 billion worth of bounty. How much remains is anyone’s guess. ...”

Read more: https://www.springfieldspringfield.co.uk/view_episode_scripts.php?tv-show=how-the-earth-was-made-2009&episode=s02e13


7 posted on 05/02/2019 4:24:55 AM PDT by ETL (REAL Russia collusion! Fake Dossier, Uranium-1 Deal, Missile Defense, Iran Deal, Nukes: Click ETL)
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To: Fred Nerks

Did a job above an old dam. The dam was supposed to have been open so we could work in the pool above the dam. I thought it would be a big deal seeing as it hadn’t been done yet. (Environmental things.)

“Oh! They didn’t tell me you wanted the water out of the pool, hold on while I open it up.”

He opened it up and all that black sand with LOTS of sparkles dropped over the edge and washed down stream. The river does hold gold, and is downstream of some deposits.


8 posted on 05/02/2019 4:31:52 AM PDT by 21twelve (!)
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To: SunkenCiv

I find your article fascinating. I also find it fascinating that most gold and other heavy metals are created by neutron star collisions.

https://www.livescience.com/60701-ligo-neutron-stars-heavy-metals-gold.html


9 posted on 05/02/2019 8:56:21 AM PDT by Moonman62 (Facts are racist.)
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To: ETL
Where would that quantity of acid come from? Acid pools like around Yellowstone? If it worked once it would work again - could we add acid to limestone and get a similar outcome?...Or is time a factor? Interesting reply...left me with more questions than answers.Thanks.
10 posted on 05/02/2019 8:58:58 AM PDT by GOPJ ("Elites reflexively exempt themselves from the ravages of their own policies." - nathanbedford)
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To: SunkenCiv

The gold mine in Cripple Creek Colorado. It is just awesome

All the rocks for miles around have some gold content as testified by the presence of many old mines

11 posted on 05/02/2019 9:05:53 AM PDT by bert ( (KE. NP. N.C. +12) Honduras must be invaded to protect America from invasion)
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To: SunkenCiv

That’s still a beautiful mineral display, even if it ain’t “true gold.”


12 posted on 05/02/2019 11:23:32 AM PDT by fieldmarshaldj (BUTTGIGGITY ! It's an anal thing. You wouldn't understand.)
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To: bert
I guess there really is gold in them thar hills.

13 posted on 05/02/2019 11:43:08 PM PDT by SunkenCiv (Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
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To: Moonman62
Thanks MM62. I do wonder what happened to all the oldtrons though. ;^)

14 posted on 05/02/2019 11:44:22 PM PDT by SunkenCiv (Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
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To: ETL; mad_as_he$$
Thanks!

15 posted on 05/02/2019 11:49:49 PM PDT by SunkenCiv (Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
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