The 2013 discovery in California of the Saddle Ridge Hoard of U.S.
gold coins reflects people’s penchant for hiding, burying or otherwise
concealing their coin collections. This is by no means new. Periodic
discoveries of caches of coins on archaeological sites in Israel,
Greece, and England show that the practice of burying coins to protect
them from theft has gone on for millennia.
I recently received an email from a longtime reader:
“A friend is considering burying some of his coin collection in his
backyard. Although he has a safety deposit box, he fears that the
government could confiscate his collection at some point down the road
as President Roosevelt did in 1933. He said he will use an air-tight,
water-proof box. Is this really a good idea?”
The short answer is no. I cannot think of a more harmful and
inhospitable environment for housing coins than to bury them
underground. Essentially you are creating an archaeological site in
your backyard and turning your coins into artifacts. The burial
environment is harsh and little of what is buried actually survives.
If an object does survive, its condition will not be the same as
when it was buried. Burying a coin subjects it to a wide variety of
environmental factors that can affect its stability and survival.
The rate at which a buried coin degrades depends on the type of
soil, its porosity, pH and salinity. The metal or alloy of a coin is
also important. The main reason the Saddle Ridge Hoard coins survived
burial so well is that they are gold.
Gold is a noble metal and, as such, corrosion resistant. You will
note that the tin cans that held the coins are corroded. Tin cans are
made from steel that is coated with a thin layer of tin. The tin
provides a physical barrier, protecting the steel from corrosion. Once
this layer is compromised, the underlying steel will corrode.
Also consider that putting gold coins in a tin can sets up a
corrosion cell. When dissimilar metals are in direct contact, the
baser metal will corrode preferentially.
Even if the reader’s friend does manage to create a water-tight,
burial-resistant container, a risk of condensation forming inside
exists when the temperature outside drops. He should also consider
flooding, earthquakes, frost heave, burrowing rodents, and
neighborhood dogs. Finally, there is the issue of retrieval. Will he
remember where he buried the coins? Will he share the location with
his family? All are important considerations.
On a completely different note, I will be participating in the Coin
Grading and Preservation Workshop Aug. 12 in Mississauga, west of
Toronto, at the Royal Canadian Numismatic Association show.