Monday, July 6, 2015

7/6/15 Report - Corroded Silver Coins. Corrosion As A Clue. Coins and Layers of Sand.

Written by the TreasureGuide for the exclusive use of

 As you know finds come in a variety of conditions.  Some come up looking like they were lost yesterday and some barely survive.

Of course some were lost just yesterday, but some that were lost long ago, still look very good, while others that aren't as old have deteriorated to near nothing.

Silver shipwreck cobs are the same way.  Some show great full detail, while others are worn away to just a fraction of what they once were. The two sides of the same coin can be very different too.

It is very common for cobs that are found on an ocean beach to have lost as much as one third of there original weight.

As I said yesterday, I've been looking at some old finds that I never really looked at very well.  In that group were a good number of Rosies and Mercs in various conditions.

Here are two of the Mercury dimes in not terrible condition.

As you probably know, silver tends to turn black, especially when it has been in sea water.

On the other hand, silver dimes that I've found in cold fresh water lakes up North, have a more gun metal blue patina and very little erosion.

The two mercury dimes above were found on Florida ocean beaches.  I don't recall exactly where.

The second one (1934) is more corroded than the top one (1941) and shows sand still adhering to the surface.

The third is also a silver dime.  This one is much more corroded.   You can't tell if it is a Rosie or Merc or what.  It does appear to be a dime though.

Notice that it also has sand still adhering firmly to the surface.  That tends to cause a mottled rough surface that is very commonly seen on more corroded silver dimes that come from an ocean beach.

I went through several that looked like this yesterday, as well as some that were worn paper thin and some that were worn completely through in some places.

Those that were paper thin were either still round though.

Some reales show the same type of corrosion.  This half reale was found at Jupiter and has one very crisp side.  The side shown in the photo was completely covered with a thick shell crust when it was found.  The other side had no sand sticking to it and that side was completely visible when dug, but the details aren't as crisp.  It seems the sand shell on the one side protected and maintained the surface of the reale.  After the sand shell was cleaned off using Muriatic acid, I saw what you see here.

Exactly how one side was so heavily encrusted and the other side not at all, I don't know.  My theory is that it rested in the sand dunes for hundreds of years unmoved.  It is hard to explain how one side attracted sand and the other side not at all.  Other cobs have been found paper thin, but still showing good detail.

Here is an uncleaned dime, which seems to have lost silver in a way that is relatively unusual for a silver dime.  They often maintain the round shape even when severely corroded.  I've seen very few silver dimes that have lost the round shape like this one.

On this one you can still make out some of the detail on the side shown in the photo.  There is no detail that can be seen on the other side.

If you look at the amount of wear, or lack of wear on a piece of silver, you might get some clue about where it has been.  If you can figure out where they have been, then you will better know where to look to find more.

Unfortunately I don't know now where these dimes came from.

I do know exactly where the half reale came from, and I am pretty sure that it just washed out of a sand dune before it was dug up.  I suspect that it was in the dune undisturbed for hundreds of years.  Undoubtedly in that time it was washed over by sea water at least a few times.  Perhaps that accounts for how one side got encrusted but not the other.

My main point today is that if you pay attention to your finds, you might get some clue to the source and therefore know where to look for more.

I suspect that coins that lose a lot of material, like the irregular shaped dime shown above, at some point was in the churning sand in the shallow water.  In contrast, I am pretty sure that was not the case for the half reale.

As a side note, I've coins found in acidic black soil around mangrove trees really corrode and dissolve.


A few days ago you saw in this blog how old shipwreck coins and items were found using blowers near shore.  A good bit of sand had to be moved to expose those items.  There are two ways that such items would have ended up under feet of sand.

Items that were lost during a hurricane might have been lost when tons of sand had just been removed and found their way down to near bedrock right away.

The other way is that items could be lost on top of layers of sand, either in the water or on the beach or on the dunes, and then gradually found their way to lower levels over the years and centuries.

Each time a layer is removed, the objects go deeper.  Sometimes they are covered again by new layers and remain there under the new layers until new erosion removes sand to deeper depths.

And of course there are times when coins and things are washed up with the new sand.  The coins that most recently washed up will then be in layers of sand above those that were in layers that previously eroded.


It looks like the surf on the Treasure Coast will be just a touch bigger this week, but not very much at all - it is still a smooth surf.

Happy hunting,