Horn Silver

NGC probably does not denote it. NGC Ancients actually leaves a lot of information off the slabs, so I doubt they would mention horn silver.

Also, as NGC Ancients tends to overgrade ancient coins anyway, I doubt anything but the worst incident of horn silver would get them to reduce their grades on one.

If you are going to go down the NGC Ancients route, worry more about misattributed coins, overgrade, hoard names that are a cheap marketing ploy and have no scholarly basis, and surface/strike grades that are woefully inaccurate and fail to take into account things like off centered strikes, weak areas in the strike, etc, and the lack of authenticity guarantee, plus the added expense of buying an encased coin over a raw example. Not to mention that the labels fail to accurately describe the coins with all the necessary information to understand what you have, plus the lack of referencing to any catalogs.

Don't get me started on WINGS stickers on ancient coin slabs and all the other little gimmicks popping all over the place designed to part a fool from his money.

 

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So... unsurprisingly, it looks like NGC doesn't specifically mention horn silver on the slab.

Some examples in which the presence of horn silver was confirmed by my eyeballs (and by the auction description ):

https://coins.ha.com/itm/greek/anci...1627-61021.s?ic4=GalleryView-Thumbnail-071515 Surfaces grade 3/5

https://coins.ha.com/itm/greek/anci...3046-31147.s?ic4=GalleryView-Thumbnail-071515 Gnarly coin; it has more surface problems than just horn silver. It's NGC surface grade was 1/5, which was deserved.

https://coins.ha.com/itm/roman-impe...1617-64092.s?ic4=GalleryView-Thumbnail-071515 In a bulk submission slab, so no surface grade is given

https://coins.ha.com/itm/greek/anci...3037-30861.s?ic4=GalleryView-Thumbnail-071515 A $41,000 coin, slabbed, surfaces grade 2/5; no mention of horn silver but the slab does indicate "edge marks"

... etc

 

"Horn Silver" is a nice name for corrosion. Shipwreck coins have it too. It destroys the original surface completely. If I remember, on Tuesday I'll post some ElCazador coins with it.

 

Perhaps it's semantics-- or maybe just my lack of education on the matter-- but I think of corrosion as material subtracted from the coin. Horn silver represents an addition.

 

When a metal corrodes, it combines with another chemical entity such as copper to sulfur to produce copper sulfide, so the resulting corrosion site would cause a gain in mass. There are some resulting compound that may not adhere as well to the original metal ( coin) and flake off, or have a lesser hardness, and friction would remove from the coin, but if all of the products were collected and weighed, the mass would be greater than the original metal ( coin). Doesn't apply to some radioactive metals, but it would take a long time to measure, and thankfully there are no coins circulating of such

 

It also depends on the type of corrosion. There are oxidation reactions where mass is lost, and there are reduction reactions where mass is gained. This is more likely with galvanic corrosion, where two different metals are in contact with each other (I would suspect that this type of corrosion would be common in hoard finds with copper coins in contact with silver coins).

 

Yes it does need clarification. I have always used Vagi's since I feel he does a good job of differentiating burial conditions. From his book coinage and History of the Roman Empire.


Perhaps geologist have a different metric, but I think collectors use a definition similar to this.

 

Oh, so it is silver deposited from other coins? I guess I was thinking it was the silver of the coin itself reacting (similar to the AgS process of toning), not added from other coins. That is interesting.

 

It was my understanding from Vagi's book that horn silvering was the migration of silver from one coin to another, through chemical processes aided by elements in the soil, but this doesn't necessarily mean that it's just elemental silver that's been deposited on the neighboring coin. Note that Vagi writes "...silver from one coin and re-deposit it in a modified form..." so this could refer to AgCl deposits on the neighboring coin.

 

My experience with Horn Silver has not been good. It comes off easily but usually leaves the surface under it worse looking than the Horn Silver was in the first place.
The coin below is not fourree but once had horn silver. While I agree it can be deposited on a coin from a neighbor, there is no reason it can not modify silver from the coin itself and removing it then should leave an ugly surface. I would prefer the coin below if it still have a dark deposit along the nose and tripod but a previous owner removed it. I bought the coin from NFA many years ago. I'll bet the cleaner paid a lot more for it than I did.

 

So all the pitted areas are where the horn silver was removed? That is unfortunate....

Newb alert.... fourree?

 

"By definition, a fourrée is made from a base metal core covered with silver foil and struck to look as if it were solid silver."

Generally, fourrées are ancient counterfeits, but not always.

 

Actually sometimes Indium, which is slightly radioactive is found in some LRB alloys; there is, however, no need for concern as it is exceptionally small amounts.

Metallurgy of Constantinian "Bronzes"

 

So don't carry them in your pants pockets should you want children...

 

I honestly don't know but I wouldn't send an ancient to NCS. If you're going to pay to have someone clean an ancient coin you want someone who specializes in ancients.

 

Corrosion eats into the metal leaving pits. By products of corrosion can be raised around or on top of the reaction site. It is all corrosion to me and can be red, black, green, brown or gray (horn silver), depending on the metal being corroded.

No one I know ever did; however, I suppose a nice even coating of HS will be more appealing than a splotchy one.

While removing it, if it flakes off, the surface underneath will be dull. If you are not careful, the slightest contact on this micro-powdered surface will leave a fresh scratch as new silver is exposed. Mechanical abrasion will remove all but the most solidly attached debris and leave you with a harshly cleaned coin.

It is best to leave these coins alone. Even professional conservation using electrolysis cannot restore a damaged surface.

 

But maybe a surgery-free alternative to a vasectomy?

 

LOL

 

There would be certain advantages, though -- like increasing the velocity of money, and discouraging hoarding.