What causes red spots on gold coins.

Reading Time: 7 minutes

Summary: The appearance of red spots on gold coins stems from known factors such as the presence of copper in the alloy, reactions with sulfur, and possible interaction with metallic dust. Despite concerns about authenticity, these spots do not devalue the coin as they’re associated with the coin’s composition and historical minting practices. Moreover, techniques like using jewelry cleaner might offer a solution for those wanting to restore the coins’ original appearance.


  1. Red Spots Origin: The red spots on gold coins, often termed “copper spots,” result from various factors like the presence of copper in the gold alloy, reactions with sulfur in the atmosphere, and potential interaction with metallic dust. These spots, despite concerns about authenticity, are commonly linked to known elements within the coin’s composition.
  2. Impact on Coin Purity: Despite suspicions, the red spots do not affect the intrinsic value of gold coins. They occur due to the presence of copper or, in some cases, tiny traces of silver within the gold, particularly in vintage coins, showcasing these discolorations as a historical occurrence rather than a sign of counterfeit.
  3. Removal Possibility: Although red spots may cause worry among collectors, they don’t diminish the gold’s value. Techniques like using jewelry cleaner can potentially remove these spots, offering a means to restore the coin’s original appearance for concerned collectors.

What causes red spots on gold coins?

Red spots on gold coins are a result of diverse factors, including the infusion of copper in the gold alloy, reactions with sulfur in the air, and the presence of metallic dust. These spots, often termed as “copper spots,” indicate areas with a higher copper content, displaying a hue that deviates from the coin’s typical yellow to take on a reddish tone. Even coins like the Gold Philarmoniker in 1/10 oz and 1/4 oz, or the esteemed $50 American Buffalo gold proof directly from the US mint, exhibit these peculiar spots, sparking curiosity about their nature and impact on value. The prevailing assumption for these marks on fine gold items, bars, or coins, has been attributed to minuscule specks of copper (a mere fraction of the overall gold purity) reacting with the atmosphere upon exposure.

red spots on gold coins can sometimes puzzle collectors.

It’s a result of various factors that can occur during the minting and handling processes. Picture this: as coins are being minted, there are numerous opportunities for contamination, machines releasing tiny particles of lubrication into the air. These particles can settle on the surface of the coins, leading to discoloration over time. Concerns naturally arise about the authenticity of these coins due to these markings, leading to questions about their legitimacy. However, the heavy concentration of copper within specific regions of the coin is a known phenomenon rather than an indicator of counterfeit coins.

The discussion extends to the gold maple varieties, questioning the purity levels, as traditionally, .9999 gold is the standard observed for gold maples. Yet, instances exist where even coins with such high purity exhibit similar discoloration due to minute traces of copper in localized areas. These spots, stemming from the presence of copper amidst the gold composition, mirror a common occurrence in vintage gold coins minted for circulation before 1933.

Moreover, the introduction of metallic dust onto these coins, especially if they’re struck and then enclosed in plastic, can also contribute to the appearance of red spots. Despite their presence, these spots don’t affect the intrinsic value of the bullion products since they have no bearing on the actual gold content. Techniques such as careful use of jewelry cleaner can potentially remove these marks, offering a solution for those seeking to restore the coin’s original appearance.

Exemple : Copper spots on mint sealed Gold buffalo

Ultimately, while the red spots might raise questions about the coin’s authenticity and cause concern for some collectors, they are a known outcome resulting from specific elements within the gold composition and external environmental factors, rather than an indicator of counterfeit coins or compromised value.

How to remove red spots on gold coins or bars, often referred to as ‘copper spots,’ can be addressed through a simple removal method involving hot water and baking soda. This process, using a shallow bowl lined with aluminum foil, involves placing the coin or bar inside and covering it with baking soda. Pouring boiling water over it initiates a sizzling reaction, which can be repeated on both sides of the item. However, a query arises concerning red spots occurring within encapsulated coins.

Exploring Color Variations and Red Spots on Gold Coins and Bars by Youyuber
Campbell’s Coins.

Campbell’s Coins shares an experience with a 2011 gold maple purchased from a reputable dealer, encapsulated a year later, developing a red spot despite the tightness of the capsule. This prompts speculation about the coin’s inability to ‘breathe’ within the capsule, potentially causing these red spots. The speaker showcases various gold coins with color variations, attributing these differences to the metals mixed with gold in different compositions. Furthermore, the discussion touches on the additional metals incorporated into jewelry for strength, which can also influence the color and composition of coins. Moreover, the video delves into the misconception of red spots signifying counterfeit gold, elucidating that these spots, caused by surface contamination during minting or encapsulation, do not necessarily indicate counterfeit items. The content emphasizes the importance of testing precious metals and the credibility of sources when making purchases.

How to prevent rust spots from appearing on gold coins?

To prevent rust spots from appearing on gold coins, it’s important to understand that gold itself does not rust or tarnish due to its non-reactive nature. However, the presence of other metals, such as copper or silver, in the gold alloy can lead to the development of red or brown spots over time. These impurities can be fixed into the coin during the striking process and may not be obvious initially. While it’s challenging to prevent these spots from appearing, storing and handling gold coins in a controlled environment with low humidity can help minimize the risk of tarnishing. Attempting to clean the spots is not recommended, as any type of cleaning can be abrasive and may reduce the grade of the coin. Therefore, it is advisable to leave the coin as is if it shows spotting imperfections.

These spots occur due to trace metals like silver and copper mixing imperfectly with the 99.99% gold composition. Unfortunately, there’s no foolproof prevention method for these spots, and while careful removal is possible, recurrence is common. Although some attribute this to rust from a die, the spots’ reappearance remains an issue.

Source image : cointalk.com

Impurities in gold coins can result in occasional red spots, though they don’t affect the coin’s weight. Some collectors even appreciate these spots. Over time, copper spots may appear on gold coins, while silver coins develop milk spots, and copper spots can affect gold coins. It’s crucial not to attempt cleaning, especially with pure metals like 24k gold. Exchanging for a spotless coin is an option, but it’s important to note that even if spots are removed, they can reappear later.

The suggestion of returning coins for replacements becomes less effective considering that a new coin might not show spots initially, but there’s no guarantee it won’t develop them later. This uncertainty makes returning problematic once spots emerge after purchase.

What are milk spots on gold coin?

I’ve noticed milk spots on several silver coins, mainly Canadian maples and British Britannias. It’s frustrating because these spots diminish the premium value of the coins, and most shops only offer to buy them at the base metal price. I’m aware that this issue stems from the minting process, involving planchets, etc. However, I haven’t see evidence about milk spots appearing on gold coins. Though copper spots are not uncommon on 24k buffalos. At first, I believed milk spots were exclusive to silver. Milk spots are white, milky marks that can appear on the surface of silver only coins and bars. These marks resemble dried milk and can vary in size and shape. They are more commonly found on silver bullion coins with a purity of 999.0 or higher and are believed to form during manufacturing as a result of chemicals used during the minting and annealing process. There is no definitive way to prevent milk spots, but storing and handling coins wisely can help. While milk spots do not affect the resale value of silver bullion coins, they may concern collectors of proof coins, as these coins are often purchased at a higher price due to their numismatic appeal. Attempting to remove milk spots is not recommended, as it could lead to damaging the coin and replacing the spots with small scratches that could worsen its appearance. The value of bullion coins is not affected by milk spots, as the coin business sees silver as silver, regardless of the marks on the surface.

The only preventive measure seems to be buying newer Canadian Maple Leaf silver coins with MintShield. I’m not sure why other minted coins or bars don’t have similar coatings.

Is it possible for gold to develop milk spots like silver?

From what I know, gold doesn’t typically experience milk spots or tarnishing like silver does. Even 24k gold, which is highly pure, may have minimal copper content that could result in copper spots—those small red points or streaks. I’ve seen copper spots on non-24k gold, particularly on old 22k sovereigns. Despite being 99.99% pure, there’s still that 1 part in 10,000 that might contain copper or silver. So it’s not impossible to have a milk stain opn a gold coin but it’s really higly improbable  Milk spots, as far as I understand, are manufacturing side effects—little white spots that appear on coins, different from tarnish. I used to think milk spots wouldn’t develop over time, but now I’m reconsidering that notion. It seems they might emerge later on.

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