"Does the silver coin has any oxidation defects?"
I believe
this kind of question is quite common for us especially you are
enthusiastically in commemorative coin collection which is always claimed as
the new growing collection theme in our nation.
What is oxidation? Oxidation is defined as the interaction between oxygen molecules and all the different substances they may contact, from metal to living tissue. Although, I can't deny the possibility of oxidation may happen on silver, but as we know that silver is actually a kind of noble metal. In other words, silver is less reactive with other elements in general and silver oxide is always appeared in grey. Thus, white stain defects on the surface of silver coin is likely not because of oxidation.
Therefore, "oxidation" may not the right term that reflects the real ground. This kind of symptom is always known as "milk spot" in Numismatic Bibliography.
Lets us have a read on how the industry players' comment regarding this issue:
- Milk spots are very common on silver coins and bars, it happens when condensation reaches the silver. (Silver Gold Bull)
- Milk spots are opaque, cloudy blemishes that can appear on silver coins after they have left the mint. Milk spots have been attributed to a range of potential causes. In our experience the exact reason is difficult to pinpoint, with recent analysis effectively ruling out crucible contamination and water quality issues. (The Perth Mint Australia)
- Planchet cleaning and preparation process may be the causes for milk spots on its coins. (Royal Canadian Mint)
In conclusion, there is no any solid evidence insofar which manage to describe the root cause of milk spot. Milk spot is not merely found
on silver, it may also illustrated on gold and copper coins. In general,
silver and copper are more frequent in facing in problem compared to gold coin.
How the "milk spots" affect the numismatic value? Professional Coin Guarantee Service, PCGS has given us the best answer.
"Spots on gold coins, spots on copper coins, and "milk spots" on silver coins are not really part of eye appeal, but they are part of the grade and grade deductions are made similar to those made for marks or hairlines. In all three instances above we have minimum/maximum grade guidelines for spots. Note that in some instances, spots can appear subsequent to grading. In the case of copper coins, the spots would result in a grading deduction, and, since there are often environmental factors beyond our control, PCGS does not guarantee against downgrades for spotting on copper coins. For modern silver issues, spotting is a Mint acknowledged problem that is also beyond the control of PCGS. For modern silver coins, it is possible for two coins to have the same technical grade and one be spotted and one be spot-free. In these instances, the spotted coins will command a lesser price in the marketplace. "
