2 lbs 13 oz Electrum Nugget.

[4metals]

It will start glowing next, just before it flies home.

Which will be soon if it has to catch up with Oumuamua, the mothership.

 

[MorrisTheProspecter]

It already flew home.

 

[goldshark]

The nuggets I posted in " metal detector screaming at pyritic ore" thread, under metal detecting, is considered Electrum. It assays .761 Au, rest Ag. with less than 1/2% Cu. Quite a bit of difference from what you have, but then again, you have more Ag, if there is anything in it at all. Just curious how you find the compositions of your rocks. Are you psychic?

 

[JMC2]

It's a very interesting specimen looks like it would be mostly silver ? Since to my eye I see little or no visible gold color. If you have other material from the same source you may want to have an assay done. I think you should shop it around and see if you can find a buyer.

For electrum (Au-Ag) alloy , you likely wouldn't see gold color from 20 percent silver or more, which is why the trade tends to define electrum that way. It would be a green gold from there to about 45% silver or so. At that point it would become silvery white---look similar to silver. And, the green color of electrum is very subtle compared to green gold alloys typical of today's jewelry trade. They add other things, Cu, Zn, and maybe 2-4% Cd (Cadmium) for deeper greens and other properties, although 75% Au-25%Ag is an alloy sometimes listed as "soft green gold." Soft because the silver doesn't harden the alloy like Cu would. Greenish electrum ranges from pale yellow-green to silverish with a green tint. The ancient Greeks called electrum white gold. Likely because the ancient Lydian Greeks made the first coins with around 50/50 electrum that would have looked silvery white.

Now this 20% Ag electrum thing is not a technical definition, it's just like an internet-spawned custom. Lots of written sources define 15% Ag or more (with little Cu) is Electrum. Some say "Electrum is an alloy of gold and silver that varies in its natural state between 65% and 85% gold." This makes sense because these points can be approximately seen by color as above.

My understanding is native yellow gold can average 12-15% Ag. Placer and plenty of rich deposits maybe less Ag but much more than 15% Ag becomes rare natively due to the workings of the Au-Ag system in deposition. This would explain why people think electrum is rare. The ancient Lydians were said to pan electrum from the river that ran through town. Ancient sources often claimed it was 50/50 (and so some people consider electrum 50/50 thereabouts the definition of electrum.) Archaeologists have had no success finding any such native alloy there (Turkey) and some books say this alloy is impossible but 55-60% Au Electrum is known from Comstock. My understanding is that prospectors still sometimes find silver-colored gold nuggets in that region. The verbose point is that electrum can be found that looks like silver instead of gold.

The more we have studied electrum, the more it seems electrum is very confusing because most think it's more than a name for an alloy and that the distinction between native gold and electrum seems arbitrary anyway.

We agree with Eion MacDonald (Nature and History of Gold, 2007) that any Au-Ag alloy (trace copper--Eion says less Cu than Ag) can be considered electrum. He also allows for native gold. But then, most think electrum can only be native gold. They say anything made is green gold--usually we would agree since they most often are at least going to add some copper to harden the alloy.

Prospectors refine the silver (and OS) out of the gold. Jewelry suppliers add back mainly copper and a little silver and other stuff (OS) to the refined gold plus deoxidizers because copper likes to oxidize causing jewelers problems. Then, for our research purposes on ancient gold and technology, scrap gold has to be refined again so that we can add mostly silver back to it to reproduce the native golds used by the old timers (say 4,000 years ago). Since these are all Au-Ag with traces of Cu and other stuff, it makes sense to think of them as electrum alloys as opposed to modern gold alloys of the Au-As-Cu system, where Cu>Ag with rare exceptions, maybe.

That's a lot more than you probably care to hear about electrum but it made sense to put it all in one placer. It is important and this is why I came here. That native gold is Au-Ag rather than Au-Cu is what allowed the ancients to work gold. No borax, no UPS bearing crucibles, no gas or electric furnaces. The old timers we studied found or dug a hole in the ground for an impromptu charcoal furnace. Charcoal had its advantages and allowed some refinement. Native/electrum was more workable, allowing the goldwork of the primitive tech Copper-Bronze Age possible.

We've made a shed full of hard-wood charcoal over the past year. We're old and slow about it all. But, we are pretty keen on electrum. Now, I gotta go dig a hole and call it a furnace.

 

[Yggdrasil]

For electrum (Au-As) alloy , you likely wouldn't see gold color from 20 percent silver or more, which is why the trade tends to define electrum that way. It would be a green gold from there to about 45% silver or so. At that point it would become silvery white---look similar to silver. And, the green color of electrum is very subtle compared to green gold alloys typical of today's jewelry trade. They add other things, Cu, Zn, and maybe 2-4% Cd (Cadmium) for deeper greens and other properties, although 75% Au-25%Ag is an alloy sometimes listed as "soft green gold." Soft because the silver doesn't harden the alloy like Cu would. Greenish electrum ranges from pale yellow-green to silverish with a green tint. The ancient Greeks called electrum white gold. Likely because the ancient Lydian Greeks made the first coins with around 50/50 electrum that would have looked silvery white.

Now this 20% Ag electrum thing is not a technical definition, it's just like an internet-spawned custom. Lots of written sources define 15% Ag or more (with little Cu) is Electrum. Some say "Electrum is an alloy of gold and silver that varies in its natural state between 65% and 85% gold." This makes sense because these points can be approximately seen by color as above.

My understanding is native yellow gold can average 12-15% Ag. Placer and plenty of rich deposits maybe less Ag but much more than 15% Ag becomes rare natively due to the workings of the Au-As system in deposition. This would explain why people think electrum is rare. The ancient Lydians were said to pan electrum from the river that ran through town. Ancient sources often claimed it was 50/50 (and so some people consider electrum 50/50 thereabouts the definition of electrum.) Archaeologists have had no success finding any such native alloy there (Turkey) and some books say this alloy is impossible but 55-60% Au Electrum is known from Comstock. My understanding is that prospectors still sometimes find silver-colored gold nuggets in that region. The verbose point is that electrum can be found that looks like silver instead of gold.

The more we have studied electrum, the more it seems electrum is very confusing because most think it's more than a name for an alloy and that the distinction between native gold and electrum seems arbitrary anyway.

We agree with Eion MacDonald (Nature and History of Gold, 2007) that any Au-As alloy (trace copper--Eion says less Cu than Ag) can be considered electrum. He also allows for native gold. But then, most think electrum can only be native gold. They say anything made is green gold--usually we would agree since they most often are at least going to add some copper to harden the alloy.

Prospectors refine the silver (and OS) out of the gold. Jewelry suppliers add back mainly copper and a little silver and other stuff (OS) to the refined gold plus deoxidizers because copper likes to oxidize causing jewelers problems. Then, for our research purposes on ancient gold and technology, scrap gold has to be refined again so that we can add mostly silver back to it to reproduce the native golds used by the old timers (say 4,000 years ago). Since these are all Au-As with traces of Cu and other stuff, it makes sense to think of them as electrum alloys as opposed to modern gold alloys of the Au-As-Cu system, where Cu>Ag with rare exceptions, maybe.

That's a lot more than you probably care to hear about electrum but it made sense to put it all in one placer. It is important and this is why I came here. That native gold is Au-As rather than Au-Cu is what allowed the ancients to work gold. No borax, no UPS bearing crucibles, no gas or electric furnaces. The old timers we studied found or dug a hole in the ground for an impromptu charcoal furnace. Charcoal had its advantages and allowed some refinement. Native/electrum was more workable, allowing the goldwork of the primitive tech Copper-Bronze Age possible.

We've made a shed full of hard-wood charcoal over the past year. We're old and slow about it all. But, we are pretty keen on electrum. Now, I gotta go dig a hole and call it a furnace.

It was a lot of talk about Arsenic here. Besides that ther may or may not be As in Gold ores it has nothing to do with Electrum per se?
Does it?
According to the definition used in Wikipedia it is an alloy of 20-80% Gold and 80-20% Silver with traces of Copper and other like Pt and such.
No mention of Arsenic.

 

[JMC2]

It was a lot of talk about Arsenic here. Besides that ther may or may not be As in Gold ores it has nothing to do with Electrum per se?
Does it?
According to the definition used in Wikipedia it is an alloy of 20-80% Gold and 80-20% Silver with traces of Copper and other like Pt and such.
No mention of Arsenic.

typo...working with arsenic bronze too, so expect my noggin slipped. Meant Au-Ag.

 

[Yggdrasil]

typo...working with arsenic bronze too, so expect my noggin slipped. Meant Au-Ag.

Makes more sense like that

 

[orvi]

Electrum for me (what I was teached) is native thing. And where I live, we have quite a bit of lower karat placer gold deposits. One area produced supergene gold that is ranging from 20-90% Au. You often have silver coloured flakes alongside with bright yellow flakes in one pan. So not that uncommon thing. Maybe somewhere in the world it is a rarity, here isn´t.
It is true that in placer deposits, naturally, gold "refines" itself by slow leaching of silver from the structure (mainly from the outer layer of flake). But we also have pleistocene sediments here, that retain 75% gold. Most of classic hydrothermal gold here is above 80%, some reaching more than 98%. Average is 85.