Recently, some deep-sea treasure hunters announced the discovery of a shipwreck with over 15 tons of Colonial-era coins worth over $500 million. The crew’s sponsors haven’t told where in the Atlantic they found the cache or which ship had all that loot. Though, they did note that the silver and gold coins were in good condition.
What affects the quality of shipwreck coins?
Where the ship goes down and what sort of metal the coins are made of. Coins that have been submerged for hundreds of years can end up being corroded, scratched, worn down, covered by sea life or lime deposits, or destroyed by acid conditions.
The warm waters of the tropics and the Caribbean will create most of the damage since warmer temps accelerate oxidation and corrosion. Also, these waters are the hosts for coral and micro-organisms that can encrust the coins, reducing their value, typically permanently. Cooler northern seas, such as the ones off the coast of England, where some think this treasure was uncovered, are more likely to aid in keeping all types of coins looking good.
Also, conditions on the seafloor make a huge difference. A muddy bottom could help sustain coins by enclosing and protecting them. Though, an environment of swirling sand can wear down markings and designs and cause scratches.
The depth of the wreck also is critical. Deep waters usually have weaker currents. So, the sand at the bottom doesn’t swirl around too much. Though, in some cases, sand can be a good thing. In 1857, The S.S. Central America sank amid calcium carbonate sands that aided in making the surrounding water slightly alkaline, keeping possible damaging acidity at bay. As a result, the ship’s coins were near-pristine when they were found in 1987.