Newer Coins Dissolving In The Ground

[Tom B]

I live in Northwest Arkansas and found an old park that is over 100 years old. I got permission to hunt it, and have been using an Equinox 900, and a Deus 1. I have found a lot of coins, the oldest from the 60's.

Something that I have noticed, coins from the 60's to the 1980's are in pretty decent shape, but coins from the 1990's to the present are literally dissolving in the ground.

Must be the soul mineralization, or maybe moisture in the ground, we get a lot of rain. We don't get inches per year, we get feet per year.

When I lived in Arizona, most coins that I found were in really good condition, maybe because of low moisture in the ground.

[F350Platinum]

I'm sure a more knowledgeable person will step in, but yeah, pennies 1982 and older hold up better than the new "Zincolns" that have much less copper. You'll see us disparaging them all the time. I throw out many of them because they're so corroded they won't take them at the bank.

Shame that 🤔

[Geologyhound]

It brings a new meaning to the term disposable income…😁

[GB_Amateur]

7 minutes ago, F350Platinum said:

...Pennies 1982 and older hold up better than the new "Zincolns" that have much less copper.

Yes, but that's about the only change since 1965.  (Half dollars were clad starting in 1965 but those early years still had 90% silver outer layers.  Starting in 1971 their composition was changed to be identical to dimes and quarters.  Dollars -- always unpopular -- have changed from cupro-nickel clad to brass.)  But other denominations (5,10,25 cents) should degrade similarly in the 1965-1989 era as the 1990-present.

The above mentioned zinc pennies (aka 'Zincolns') have an especially bad problem due to the galvanic process that causes the copper coating (only ~2% of the entire coin) to chemically react with the zinc interior somewhat like what goes on in a common battery.

[F350Platinum]

I really dislike 1965 quarters 🤬

[JCR]

They always laugh at you when you check the date.😜

[Geologyhound]

9 hours ago, GB_Amateur said:

Yes, but that's about the only change since 1965.  (Half dollars were clad starting in 1965 but those early years still had 90% silver outer layers.  Starting in 1971 their composition was changed to be identical to dimes and quarters. 

I wondered about that.  All the online references say the 65 coins are cupronickel cladded - there was no mention of the silver cladding in the websites I checked.  I recently dug a 65 dime and quarter at the same site that I thought were silver when I pulled them out.  But they were both clad.  I was wondering if they were some sort of clad error, but with two shiny coins and no reference to silver cladding, I figured that somehow both were recently lost.

[Tom B]

In 2015, I lived in Arizona, I was in the Bradshaw Mountains, east of Wickenburg at an old miners camp and dug a 1873 half dollar that cleaned up real nice. That thing was in the ground for a long time.

I think I found it with an E-Trac, can't remember what the soil mineralization was, but I remember the ground was hard as concrete, I had to use a screwdriver and hammer to get it out of the ground. Maybe the ground being packed preserved it

[CPT_GhostLight]

The types of chemicals used it park fertilizers can also play havoc on coins, specially zinc pennies. I found "zincolns" in some parks from the 2000s that have deteriorated down to half a coin and in parks with milder fertilizers the 2000s pennies come out clean.

I think we should load up a truck with all the rotting zinc penies and send them to the US Mint for replacement.  They are obviously defective. 🤣

[mebeep]

Here's a link to Silver Wolverine discussing the introduction of new legislation to possibly change the metal composition of more U.S. coins.