Larry’s comment: Don’t listen to ego-centric, big mouth fools like Stewart Blay and others who pretend to be experts (they’re not) on Coin Forums, and spew a lot of inaccurate and misleading phony information that gets repeated by others equally not in the know. My strong advice is don’t listen to anything you read on an amateur forum, unless it is posted by a TRUE expert–and there aren’t very many of them!

The article below is written by one of the leading experts in the hobby. Ron Guth has a lifetime of research experience and knowledge. He is the founder and builder of CoinFacts, the leading source of on-line numismatic education for the hobby. Ron also served as President of PGCS, the hobby’s most respected grading service, for several years, before stepping down to concentrate fully on the expansion and continued development of CoinFacts. He remains one of the key components of the Collector’s Universe/PCGS management team and Board of Experts. There is no one in the numismatic universe that I have higher respect for.

The red highlights are my addition, since they are most pertinent to the readers of this site.

 

Posted on June 29, 2017 by Ron Guth, for PCGS:

When coins come clinking out of the presses at the Mint, they are pristine. Copper coins are bright red, nickel coins are flashy silver-gray, gold coins are brilliant yellow, and silver coins are shimmering white. From the moment they are struck, and as soon as they hit the atmosphere, coins begin to react chemically with their environment. As part of the reaction process, colors of various hues begin to form on the surfaces of these coins – in numismatic terminology, this is known as toning. The depth and appearance of the toning is completely dependent on how the coins are stored and to which chemicals they are exposed.

In this installment, we’ll look at the colors that appear on some different coin types. But first, let’s examine how toning impacts the grade of a coin. One of the more significant components of a coin’s grade is its eye appeal. A sub-component of eye appeal – and a significant one — is toning. Toning can be negative, neutral, or positive. Negative toning can be dark, splotchy, dull, or so deep that the surface of the coin appears to be burnt. Negative toning will lower the overall grade of a coin. Neutral toning is middle-of-the-road; not really ugly, but not very attractive either. Neutral toning will usually have no effect on the overall grade of a coin. Positive toning can be stunning, and is often described variously as “rainbow”, “iridescent”, “monster”, “killer”, or just plain “awesome” toning. Not unexpectedly, positive toning can add a lot to the overall grade of a coin, not to mention its value.

Copper coins start out as bright red. Over time, they will begin to tone to an even brown color as they move through the Red Brown phase, which PCGS defines as going from 95% Red to 5% Red. Along the way, copper coins can also pick up some interesting colors, such as blues, oranges, and purples. This is especially true of Proof Indian Cents, which often develop intense iridescent colors over time.
The color of early Large Cents can be affected by other factors, including the purity of the copper used as planchets. Several prominent collectors, including Dr. William H. Sheldon, Dan Holmes, and Pierre Fricke assembled collections of Large Cents with as many different color combinations as possible. Dr. Sheldon’s collection consisted of 66 different coins; Mr. Fricke had over 100 different examples, including red, orange, tan, green, blue, and gold colors.

Silver coins are more apt to develop colorful toning, particularly when they are near a source of oxygen and sulfur (found in most paper products). Here is where you will find a wide spectrum of colors: blues, greens, purples, reds, and golds. We’ve seen Morgan Silver Dollars with weave-pattern toning from the canvas sack in which they were stored. Some of the Redfield Hoard Morgan Dollars were spattered with juice from exploding cans of peaches, which often led to some interesting toning.

“Tab” toning refers to some of the commemorative issues that were slipped into paper packets for sale to collectors, then stored that way for years. Aficionados of toned coins often pay huge premiums for coins with wild color schemes. In 2016, Legend Rare Coin Auctions sold the Northern Lights Collection of toned Silver Dollars. One of the highlights was an amazingly toned 1881-S in MS66 that sold for $7,050 – or 28 times the PCGS Price Guide for a regular MS66!


Copper-Nickel coins tend to be relatively inert
, but they will also pick up colors depending on how they are stored. Gold is another inert metal, but because it is often alloyed with copper, such coins can develop either undesirable red spots or desirable reddish toning. If you are not a fan of toning and wish to avoid it altogether, stick with the modern platinum or 99.99% fine gold coins – they will never tone or tarnish.

Here’s one important caution as you seek out toned coins: to avoid the trap of artificial toning, stick with PCGS-certified coins. Our experts are very good at discerning the difference between original and artificial toning, plus each certified coin comes with the PCGS guarantee.

PCGS is the premier authentication and grading service for U.S. and World rare coins, and the premier internet web site for rare coin information and education. To learn more about PCGS and their services visit www.pcgs.com or www.pcgscoinfacts.com.