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Colors of US gold coins
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47 posts in this topic

55 minutes ago, GoldFinger1969 said:

It's not the variance in gold or copper/silver that led to luster/shine/gold color......it was the dies and the strike, right ?

This isn't lighting I believe, it's the coin and the gold.  Best-looking Saint I have seen via pics.

1908-S MS67 Duckor-Norweb.jpg

[Now I understand your affinity for this particular coin.]

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3 hours ago, RWB said:

1630Boston, member on another forum, posted “Please tell me what causes the difference in the color of Gold Coins.” This was based on an 1887 letter in the NNP US Mint files and transcribed by NNP. Another member posted a link to a web site that was presented as answering the question.

First, collectors should understand that multiple factors affect the original color of US gold coins, Second, after about 1847 all U.S. gold coins were made from refined metal of 0.999 fine. Third, objective evaluation of coin color requires attention to detail and neutral viewing conditions. Always evaluate the color of a coin under standard daylight and 18% gray backgrounds. All uncontrolled light must be blocked, otherwise the color your eye perceives will be inaccurate.

1.      Early years. The U.S. Mint had very limited gold refining capabilities. Nearly all gold was derived from foreign coins deposited at the Philadelphia Mint. The Melter & Refiner then added fine gold to bring the alloy up to standard, or added copper to reduce the fineness to the same standard.

2.      The normal alloy was a mixture of copper and silver with a maximum of half the alloy being silver. Under ideal conditions, this produced a slightly light gold colored coin. If more than half the alloy was copper, the coins became a little darker, with an increasingly orange tone. If all the alloy was copper – as with melted French or British coins – the gold pieces had more of the color of double eagles from the 1870s and 80s.

3.      The reason for this odd alloy was to permit standard gold coin to be made from a wide mixture of foreign coins and limited native gold dust. It also helped to obscure trace element contamination, which was very common at that time. Refining (and assaying) were not of the quality in later commercial use.

4.      Another factor was the fuel used to melt gold, silver and copper. Coal was always contaminated with sulfur which got into the crucibles and formed compounds with both silver and copper. Oxygen combined readily with copper, and available fluxes were unable to absorb all the oxides and trace contaminants.

5.      Due to contaminants and the unstable alloy mix even such minor things as stirring/mixing the melt, and the time to ladle or pour ingots could produce slight variations in coin color.

6.      French indemnity gold and later California gold pushed the Mint toward using only copper for alloy, and insisting on only copper of the highest purity. (Much came from a Baltimore company.) Doing this made ingots more consistent, less brittle, and melts more uniform – resulting in better coin quality with less wear on dies and equipment. Southern state gold and then California gold also pushed the Mint to adopt much better refining methods. Californian gold was especially troublesome because it often contained platinum, iridium and osmium in measurable amounts, and these had to be removed before the gold was pure enough for coinage use.

7.      From about 1847 US gold coins were more uniform in color and had become the somewhat orange-gold color associated with double eagles. Melting remained dependent on coal so sulfur still contaminated copper. When gas-fired furnaces were gradually put into use in the 1890s there was much less sulfur and the coins settled into a stable orange-gold color.

8.      Coins using silver in the alloy can sometimes take on a slightly greenish cast from multiple silver species and interaction with copper compounds. 20th century sandblast proofs – primarily undipped pieces – can look greenish because of ambient fluorescent light reflections.

This little note should help members understand about the color of gold coins.

Your mention of the presence of the element Osmium "in measurable amounts" [par. 6] is noteworthy. In contrast to Lithium which is the lightest metal, #3 on the Periodic Table, Osmium is the densest at atomic #76. (I recognize there is a difference between density and weight.)

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2 hours ago, Quintus Arrius said:

[Now I understand your affinity for this particular coin.]

That 1908-S....that color just BLAZES out at you.  Even someone who only has experience with pocket change can see the luster and shine on that baby. xD(thumbsu

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7 hours ago, GoldFinger1969 said:

That 1908-S....that color just BLAZES out at you.  Even someone who only has experience with pocket change can see the luster and shine on that baby. xD(thumbsu

A coin is merely deformed metal. The appearance is altered by dies and their surface condition during striking. "Color" is not to be confused with surface reflections, light scatter, etc. Post production conditions can alter the appearance including color.

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1 hour ago, RWB said:

A coin is merely deformed metal. The appearance is altered by dies and their surface condition during striking. "Color" is not to be confused with surface reflections, light scatter, etc. Post production conditions can alter the appearance including color.

Yes, I found your explanation of "luster" in the book fascinating.  I always thought it was an indication of smoothness, and in fact it's microscopically rough surfaces that allow light to reflect.

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1 hour ago, GoldFinger1969 said:

Yes, I found your explanation of "luster" in the book fascinating.  I always thought it was an indication of smoothness, and in fact it's microscopically rough surfaces that allow light to reflect.

Now try to explain that concept to the Chief Moderator over at CT. He still doesn’t understand it.

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14 hours ago, GoldFinger1969 said:

It's not the variance in gold or copper/silver that led to luster/shine/gold color......it was the dies and the strike, right ?

This isn't lighting I believe, it's the coin and the gold.  Best-looking Saint I have seen via pics.

1908-S MS67 Duckor-Norweb.jpg

I think anyway this is the opposite of what RWB was getting at. First luster and color are two different things. And the color is influenced by refining technique and composition of the final metal used for the planchet. The subsequent toning after production is also influenced by composition. So color is directly related to planchet composition and post production environment. Nothing to do with dies or strike pressure. 

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1 hour ago, Woods020 said:

I think anyway this is the opposite of what RWB was getting at. First luster and color are two different things. And the color is influenced by refining technique and composition of the final metal used for the planchet. The subsequent toning after production is also influenced by composition. So color is directly related to planchet composition and post production environment. Nothing to do with dies or strike pressure. 

Yeah, that's pretty much it. The mixture of compounds on the surface alter the human perception of color, also. This is complicated by thin film interference and the colors of individual compounds that are scattered and not fully resolved by our vision.

I suggest that collectors never rely of a description or photo of a coin's colors for a buying decision.

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1 hour ago, Woods020 said:

I think anyway this is the opposite of what RWB was getting at. First luster and color are two different things. And the color is influenced by refining technique and composition of the final metal used for the planchet. The subsequent toning after production is also influenced by composition. So color is directly related to planchet composition and post production environment. Nothing to do with dies or strike pressure. 

The 1908-S above has unique COLOR and shows LUSTER to me -- so I think it's a combination of all those factors, right ?

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38 minutes ago, RWB said:

Yeah, that's pretty much it. The mixture of compounds on the surface alter the human perception of color, also. This is complicated by thin film interference and the colors of individual compounds that are scattered and not fully resolved by our vision.  I suggest that collectors never rely of a description or photo of a coin's colors for a buying decision.

Agreed, but that 1908-S stands out apart from any other Saint-Gaudens DE I've seen with the exception of the UHRs.

Always cautious on pictures -- I've been shown how lighting can dramatically change the appearance -- but assuming lighting isn't being manipulated, top-notch Hi-Def pics like those at HA can show differences in coin's appearances much much better than pics from 20 or 30 years ago.   

I'm curious as to how other top-graded 1908-S's look.  With low mintage, good chance I'll find coins struck with the same dies and/or at the same time.  I'll do some looking and see how good they look.  Also will re-read the chapter in Roger's book.

Edited by GoldFinger1969
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Some other 1908-S's had older pics in the HA archives from 2005 or thereabouts and were of no use.

But this one recently sold once again shows that lustrous bright copper red color.

1908-S MS66 CAC.jpg

1908-S MS66 CAC reverse.jpg

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Good info. I was the guy who responded on the other forum to the original question by giving a link to an article about what causes different colors on gold coins. That article was simplified, the original post here gets into some more details. 

 

 

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For clarity I'll add that photos taken through plastic holders impose their own set of defects and inaccuracies....regardless of how "good" the photographer.

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4 hours ago, VKurtB said:

Now try to explain that concept to the Chief Moderator over at CT. He still doesn’t understand it.

Huh?  As someone who has spent countless hours arguing with Doug about his numismatic lunacy, this is one topic he does understand, and he always uses the same simple diagram to show it /\/\/\/\/\/\/\/\

As for color on gold, it has long been accepted that insufficient alloy mixture, particularly at the surface was the cause.

af0ngh7.jpg

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32 minutes ago, Mr_Spud said:

Good info. I was the guy who responded on the other forum to the original question by giving a link to an article about what causes different colors on gold coins. That article was simplified, the original post here gets into some more details.

Details make the difference between an accurate, repeatable result and "heresay."

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2 hours ago, lehigh96 said:

As for color on gold, it has long been accepted that insufficient alloy mixture, particularly at the surface was the cause.

That's a generalization that is not correct. Colors on the posted DE have no basis in alloy uniformity.

Edited by RWB
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3 hours ago, RWB said:

For clarity I'll add that photos taken through plastic holders impose their own set of defects and inaccuracies....regardless of how "good" the photographer.

But presumably all coins are at an equal-disadvantage being photographed through the plastic, right ?

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4 hours ago, Mr_Spud said:

I was the guy who responded on the other forum to the original question by giving a link to an article about what causes different colors on gold coins.

Could you repost that link here ?  Thanks !  (thumbsu

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3 hours ago, lehigh96 said:

As for color on gold, it has long been accepted that insufficient alloy mixture, particularly at the surface was the cause.

So what do you think causes the differences between those 1908-S's I posted above....and a pretty bland 1924 Saint ?

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4 hours ago, RWB said:

That's a generalization that is not correct. Colors on the posted DE have no basis in alloy uniformity.

But no 2 alloys are exactly the same, right ?  So that difference from alloy-to-alloy and the source of the gold (Nevada vs. California) has to play a part in appearance.....die differences.....mechanical differences in the presses.

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48 minutes ago, GoldFinger1969 said:

But presumably all coins are at an equal-disadvantage being photographed through the plastic, right ?

No. Plastic holders differ and there is no meaningful "standard" for them. Plus, plastic physical deformation from mechanical stress can show up in photos, although it's especially clear when polarized light is used.

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47 minutes ago, GoldFinger1969 said:

But no 2 alloys are exactly the same, right ?  So that difference from alloy-to-alloy and the source of the gold (Nevada vs. California) has to play a part in appearance.....die differences.....mechanical differences in the presses.

For most US gold, that target alloy is .900 gold, .100 copper - nothing else. Legal tolerance is so small it can not be detected by sight. During melting, casting, ingot rolling, blank cutting, etc. gold ans silver were subject to multiple assay tests on each melt and then on ingots poured (dipped in many cases) from top, middle and bottom of the crucible. The last few ounces were not used at all, and simply put into the scrap for reuse.

Trace elements can be used to locate the source of native gold. By definition, fully refined gold (0.9999) has few trace elements, that is, refined gold is anonymous. Mechanical issues not included.

Old time US Mints routinely shipped gold and silver to one another to better balance regional coin demand. (called "redeposits.") The NYAO refined metal from all over the world; SF got deposits from Australia, Philippines, Alaska, Yukon, Japan.

Edited by RWB
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https://raregoldcoins.com/blog/articles/coloration-and-united-states-gold-coins

2 hours ago, GoldFinger1969 said:

Could you repost that link here ?  Thanks !  (thumbsu

above is the link I put up across the street. I found it just doing a google search a few weeks ago after someone resurrected an old thread that talked about iridium and other metals being present in gold mined at different locations that was supposed to be part of the reason that some gold coins have differing coloration. The thread got into things like if the gold assayed pure enough right out of the mines it wasn’t always refined and that played a role in some mints having coins that came out different. The thread also said some mints basically always had to refine their gold but others didn’t. It made me curious so I googled it to find more info and found the article I linked. 
 

so when the post came up I remembered the link and thought it fit in with the new post.

then I came over here and read this post and found out a bunch more details that weren’t discussed much in the 2 threads across the street. Good stuff.

 

 

Edited by Mr_Spud
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7 hours ago, lehigh96 said:

Huh?  As someone who has spent countless hours arguing with Doug about his numismatic lunacy, this is one topic he does understand, and he always uses the same simple diagram to show it /\/\/\/\/\/\/\/\

As for color on gold, it has long been accepted that insufficient alloy mixture, particularly at the surface was the cause.

af0ngh7.jpg

Then ‘splain to me why Doug insists that mirrored proofs have full luster. Mirrors don’t DO luster. 

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