How did the industrial size smelters refine the metals in the 1800's

[goldshark]

How did the smelters operating in the 1800's, refine the ores down to the final precious metals? They would have ores or concentrates, that contained practically all the base metals, plus PM's, all smelted together. Lead or Copper was used as a collector, but I know they did not have giant cupels, thereby wasting all the base metals into the cupel. Electro winning hadn't come into vogue, and they certainly didn't do it with acids. Does anybody know how this was done? Again on tons of metal per day, not on an assay ton level.

 

[nickvc]

From what I can understand they crushed the ores and used mercury and copper plates to recover the gold and silver further separation was achieved using acids, this process using Royal Water Aqua Regia was an old process developed by the alchemists centuries before.
The first gold refining was from placer gold which often had and still has silver in the mix to separate the Romans used salt , the ancient peoples were not stupid in fact far from so they learnt ways to achieve amazing things just think how the Egyptians or whoever built the pyramids or carved their statues and how the Roman’s developed concrete that lasted millennia unlike our version which decays much much quicker.

 

[Yggdrasil]

How did the smelters operating in the 1800's, refine the ores down to the final precious metals? They would have ores or concentrates, that contained practically all the base metals, plus PM's, all smelted together. Lead or Copper was used as a collector, but I know they did not have giant cupels, thereby wasting all the base metals into the cupel. Electro winning hadn't come into vogue, and they certainly didn't do it with acids. Does anybody know how this was done? Again on tons of metal per day, not on an assay ton level.

They had steam engines and other engines and they had compressors and plenty of coal.
So the fuel was side was ok, and they were smart with refractories and such.
But in many ways it was harder for them than today.

 

[goldshark]

So apparently, Either I did not communicate properly, or you did not understand my questions. After stamp milling, gravity separation, amalgamating, flotation, etc., those concentrates were sent to the large smelter. My question is really about how they got a couple of ounces of Au/Ag out of a ton of melted Pb,Cu, Zinc. The refining of the Dore' bars on an industrial scale is what I am asking.

 

[Yggdrasil]

So apparently, Either I did not communicate properly, or you did not understand my questions. After stamp milling, gravity separation, amalgamating, flotation, etc., those concentrates were sent to the large smelter. My question is really about how they got a couple of ounces of Au/Ag out of a ton of melted Pb,Cu, Zinc. The refining of the Dore' bars on an industrial scale is what I am asking.

Aah I see.
Probably some industrial version on what we do today.
Most processes was well known at that time too.

 

[goldshark]

After doing a little on line research, I think I answered my own question. The Parkes process ( adding metallic Zinc to 325-375 C molten Lead), will not only collect Silver, but Gold as well. I had heard it collected Ag only, never heard anything about collecting Au as well. Zinc is then vacuum distilled off, or vaporized and collected for later conversion back to metallic Lead. Au/Ag can then be parted by Nitric acid. There are quite a few processes out there , for the removal of a variety of metals, which are readily collected by the Lead in the smelt, after performing the Parkes process.

 

[nickvc]

I tried to answer your question and if you look at old hard rock mines many seem to have the crushing facilities and the copper plates with mercury on to collect the gold out of the concentrates, this is one of the reasons there is so much gold in streams with mercury on it.
The ancient civilizations produced gold and silver coins of known fineness for centuries often debasing them over time , sounds familiar , so the methods and processes we still use today were probably used to purify the gold but the basics of extraction from ores was mercury so low grade dore bars probably didn’t exist but high grade material was sent for refining.

 

[Yggdrasil]

I tried to answer your question and if you look at old hard rock mines many seem to have the crushing facilities and the copper plates with mercury on to collect the gold out of the concentrates, this is one of the reasons there is so much gold in streams with mercury on it.
The ancient civilizations produced gold and silver coins of known fineness for centuries often debasing them over time , sounds familiar , so the methods and processes we still use today were probably used to purify the gold but the basics of extraction from ores was mercury so low grade dore bars probably didn’t exist but high grade material was sent for refining.

I find myself in awe sometimes when I see what the ancient people
managed to do with way less sophisticated tools then us.
They were indeed as smart and resourceful as us, maybe even more so.

I find many of the old processes have an elegance and inventiveness
that is quite breathtaking despite their lack of sound
waste and risk management after today's standards

Edited for reability after posting on a phone

 

[SRM]

Years ago I did some work in Peru. IIRC just south of the of the airport in Trujillo is a pre-Inca ruins of a huge city. We got a tour of it and our guide mentioned that the purpose of many of the ruins was mystery. In one particular area (maybe an acre in size) of several buildings, he mentioned that they thought the area was for firing clay because of the many scorched clay vessels, relatively small furnaces and larger vessels of various items such as sand, charcoal, crushed seashells, salt to be used as glazes. I asked if they found copper and quartz rock here and he said they had, plus lots of really long tools and remnants of thick leather garments. I am convinced it was an early smelter for gold silver and copper. My guess was each small area specialized in a particular metal.

 

[kurtak]

How did the smelters operating in the 1800's, refine the ores down to the final precious metals?

goldshark - in the 1800s they did it basically the same way as gold smelters & gold refiners have been smelting/refining gold for thousands of years --- it is just that by the 1800s they were able to do it on a much larger scale due to advances in technology (industrial age) & improved chemistry (use of more pure chemicals)

The (known) history of gold smelting & refining goes back as far as 6000 years BC found in both ancient text (writings) & physical evidence of smelters/refiners (discovered through archaeological findings/diggings)

The earliest records date back to ancient Mesopotamia (Syria/Babylon) with smelters & refineries discovered (dug up) as well as stone/clay tablets (text) in both Arabic & Hebrew archaeological findings that date back to around 6000 BC --- as well as findings in ancient Egypt (around the same time) & China, India dating back to around 4000 - 3000 BC

Just like in ancient times - gold smelters today (&/or 1800s) did not try to smelt a few ozt of gold from a ton of ore --- they concentrated it first - that part of the process has not changed since 6000 BC (the earliest known records)

With a good concentrate - no collector metal is needed - just flux - a good concentrate is a concentrate that is at least 30% gold - in which case no collector metal is needed which even the "ancients" (Arabic's/Hebrew's) knew

The smelting process produces a dore of (primarily) gold/silver/copper) which can (generally speaking) run between 80 - 95% gold --- the next step (even around 6000 BC) was refining the dore

Before the advent of the Miller Process in the mid/late 1800s of bubbling chlorine gas through the molten gold to remove the silver/copper --- the ancient refiners used a crud forum of that process called gold cementation (not the same as cementing PMs from a solution) rather it is a high temp pyro process --- you could call it the "poor mans" miller process & is able to purify gold to 98.5 - 99.5

The ancients did this by taking the gold dore & hammering it into VERY thin foils

The thin foils would then be layered in a clay pot with salt (sodium chloride) & red brick dust (flux) & the clay pots were sealed & then placed for a day in a fire - this (heat) would then create chlorine gas (from the salt) which would go through the thin gold foils causing the silver to come out of the gold as silver chloride that collected with the salt/red brick dust & as well the chlorine would gas off the copper which was then reduced to copper oxide by the iron in the red brick dust

The slag - (salt/red brick dust/silver chloride/copper oxide) could them be re-smelted (likely with soda ash) to recover pure silver from the gold refining slags

This gold refining process took 3 - 5 days - depending on how impure the dore was to start with because after each day in the fire they would have to redo the above process 3 - 5 times in order to achieve the desired gold purity of 98.5 or better

This has all been proven through analyzing the clay pots & slags as well as gold found purified to 98.5 or better that dates back to around 6000 BC

For what it is worth

Kurt

 

[goldshark]

Thanks for the run through on the ancient technology, always fascinating to learn the evolution of our industry. Going back to my original question I would like to add that not all ores were free milling ores. Once through the oxidized zone of the deposit, the miners encountered the sulfides. They were able to produce a concentrate with other minerals, which needed to then be sent to the smelters for further refining. The concentrates were rich if they had 15 ozs. Au per ton. This would have to be blended with a carbonate hosted Pb/Ag ore to act as a collector metal, and provide the basic flux component so the mix would melt. I got all that part. The main bit of information I did not know, was the use of metallic Zinc to collect the Au and Ag from the large pool of molten Lead contained in the smelter crucible, known as the Parkes Process. I thought it collected Ag only. Thank you Kurt for the explanation for the process used before the Parkes Process was invented. I learned something new today.

 

[Yggdrasil]

goldshark - in the 1800s they did it basically the same way as gold smelters & gold refiners have been smelting/refining gold for thousands of years --- it is just that by the 1800s they were able to do it on a much larger scale due to advances in technology (industrial age) & improved chemistry (use of more pure chemicals)

The (known) history of gold smelting & refining goes back as far as 6000 years BC found in both ancient text (writings) & physical evidence of smelters/refiners (discovered through archaeological findings/diggings)

The earliest records date back to ancient Mesopotamia (Syria/Babylon) with smelters & refineries discovered (dug up) as well as stone/clay tablets (text) in both Arabic & Hebrew archaeological findings that date back to around 6000 BC --- as well as findings in ancient Egypt (around the same time) & China, India dating back to around 4000 - 3000 BC

Just like in ancient times - gold smelters today (&/or 1800s) did not try to smelt a few ozt of gold from a ton of ore --- they concentrated it first - that part of the process has not changed since 6000 BC (the earliest known records)

With a good concentrate - no collector metal is needed - just flux - a good concentrate is a concentrate that is at least 30% gold - in which case no collector metal is needed which even the "ancients" (Arabic's/Hebrew's) knew

The smelting process produces a dore of (primarily) gold/silver/copper) which can (generally speaking) run between 80 - 95% gold --- the next step (even around 6000 BC) was refining the dore

Before the advent of the Miller Process in the mid/late 1800s of bubbling chlorine gas through the molten gold to remove the silver/copper --- the ancient refiners used a crud forum of that process called gold cementation (not the same as cementing PMs from a solution) rather it is a high temp pyro process --- you could call it the "poor mans" miller process & is able to purify gold to 98.5 - 99.5

The ancients did this by taking the gold dore & hammering it into VERY thin foils

The thin foils would then be layered in a clay pot with salt (sodium chloride) & red brick dust (flux) & the clay pots were sealed & then placed for a day in a fire - this (heat) would then create chlorine gas (from the salt) which would go through the thin gold foils causing the silver to come out of the gold as silver chloride that collected with the salt/red brick dust & as well the chlorine would gas off the copper which was then reduced to copper oxide by the iron in the red brick dust

The slag - (salt/red brick dust/silver chloride/copper oxide) could them be re-smelted (likely with soda ash) to recover pure silver from the gold refining slags

This gold refining process took 3 - 5 days - depending on how impure the dore was to start with because after each day in the fire they would have to redo the above process 3 - 5 times in order to achieve the desired gold purity of 98.5 or better

This has all been proven through analyzing the clay pots & slags as well as gold found purified to 98.5 or better that dates back to around 6000 BC

For what it is worth

Kurt

I have to arrest you a bit here, I believe what they dug up was clay tablets with the sign language called Cuneiform.
This writing form dates back to around 3500BCE and was used by many civilizatons in the region.
The Babylonians/Assyrians used it for around 700 years until it disappeared.
Babylon city emerged around 2200BCE and the same time the Babylonians arrived from the west.
The Hebrew language emerged around 1900ish BCE and their alphabet in around 1800 BCE so it could in theory be on stone tablets by the Babylonian/Assyrians in the Irak/Syria region, but the Arab language did not appear until around 8-900 in north western parts of the Arab peninsula.
And their alphabet did not emerge until 400BCE, long after the Assyrians was gone.

The rest was a very interesting thing to read and make perfect sense,
and another proof that the ancients just had less tools and still managed to get the job done

 

[Heavy-Black-Sand]

How did the smelters operating in the 1800's, refine the ores down to the final precious metals? They would have ores or concentrates, that contained practically all the base metals, plus PM's, all smelted together. Lead or Copper was used as a collector, but I know they did not have giant cupels, thereby wasting all the base metals into the cupel. Electro winning hadn't come into vogue, and they certainly didn't do it with acids. Does anybody know how this was done? Again on tons of metal per day, not on an assay ton level.

From the 1,500's .....




From 500 BCE .....

 

[andu]

Their discarded/refined ore is somewhat processable nowadays if you were wondering that.