Monday, February 24, 2014

2/24/14 Report - Iron Flakes or Silver, Driftwood, & Groins and Beach Dynamics

Written by the TreasureGuide for the exclusive use of

Example of Nice Piece of Driftwood That Could Be Easily Sold
Before I get into my main topic today, you might remember that I talked a little about the market for driftwood.  Here is one of my favorite driftwood finds.

It is flat on the back and could be easily hung on a wall as is, but I have another idea for it.

You might be able to see the quarter shown for size.

A couple of days ago I posted some pictures of flakes of iron that people often ask about.

Pete L wrote and said,

  I was thinking back a few years when I found my first two 1/2 reales.

I remember vividly that both of those 1/2s looked exactly like the piece

of iron to the right of the dime in your photo!  I actually almost tossed them

but looked closely and saw the tell tale little cross in the middle of them.

  Now, whenever I find something like that i simply try to snap it in half.

If it snaps it's most likely iron but if it resists snapping there's a good

chance it's Silver!

Thanks for the good tips Pete.  Most half reales if they show nothing else will have some sign of the cross showing, but not always. 

My first Spanish silver was not a cob, or if it was it was what is sometimes called a razor because it is worn so thin and featureless.  No sign of cross or anything else could be seen on it, but it is silver.  I did an acid test on it.

Many detectors will tell you if an item is iron or silver.  And another quick test is a magnet.
I always say don't throw an item away if you aren't sure about it.  You won't regret holding onto it as much as you'll regret throwing something good away.

Two or three days ago I showed how sand moves back and forth up and down a beach with each wave and with the tides.  I said there are normally additional factors.  Today I'll address one of those additional factors.   It is long-shore, or littoral, drift, which I observed while detecting long before I knew what it was called.

Here is a simple animation that shows how sand moves with the waves and with long shore currents, assuming a straight beach line.

When you go to the link, click on the graphic to see the animation.'sl%20guide%20to%20folly%20beach/guide/driftanimation.htm

You will see that zigzag pattern while detecting near the water.  If you dig a target, in the moving water and the target falls out of your scoop, it will move either up or down the slope and in the same direction as the water north or south on the beach.  I've seen that a million times.

Sometimes I'll throw a coin into the waves on the beach just to see how they move the object.  Sometimes they'll move a lot and sometimes not as much.   I've done a lot of experimenting and observing.

If you lose something like a pull tab out of your scoop it will be moved farther than some other objects such as coins.

If you want to keep the object from moving when it is on or near the surface when a wave comes, quickly put your foot on it.  I've talked about that before so I won't repeat all of that.

Another thing you can do to keep from losing the object is to keep sweeping your coil over it and track it while it moves.

You want to know how the sand and objects are moving so you can look at a beach and get a good idea of where to spend your time.  You can learn to know where any hot spots are likely to be.

The littoral drift along the Treasure Coast as well as most of the Florida East Coast is north to south.

So what happens if you don't have an entirely straight beach, but instead there are obstructions to the flow of sand.  One good example that illustrates what happens is when there are groins.

I learned about groins a long time ago.  The sand will pile up along one groin or another depending upon the direction of the waves.  By the way, groins and similar structures create some very good hot gold spots.

Below is a good diagram from this web site.

First,notice the direction of the waves.  That is a critical factor.

Second, notice the direction of longshore transport (the direction that long-shore currents are carrying sand.) that in this illustration goes left to right.

Focus on the first two areas in between the first groins.  I don't want to get into tapered groins or other complications now.

The sand is tilted between groins, as is usually the case.  It will usually pile up more on one side but will change sides if you have a change in the direction of wind and waves for a long enough time.

When the waves come from the left they are going along with the longshore transport to some extent.  If the waves were hitting more from the right, they would be going against longshore transport.

Although I won't elaborate on that now, Ive touched on some factors that partly explains the differences between the effect of nor'easters and southeasters on Treasure Coast beaches.

As shown in this illustration, with the waves hitting as they are in the illustration, a small amount of sand will be removed from the left of the area in between groins and a greater amount of sand added to the right side of the area.

As I said, this will occasionally reverse to some extent when conditions are extreme enough.  That will uncover pockets of heavy accumulations.

Groins provide a good illustration.  A similar thing happens with coves or simple curves in the beach or other situations that cause a protected  pocket of some sort that prevents a natural flow of sand along the beach.  It could be rocks or sand bars or other things.

There are still a lot of factors I haven't added to the system.

Here is an extra reading on Cross-shore and longshore sand transport.

We are stuck with a small surf on the Treasure Coast.  That is bad for beach detecting, but it is good for water detecting and there is still gold coming from the water at swimming beaches.

Happy hunting,