Black sand beach with m6 ... Strange behavior ..

[norbyx]

Well here is what happened to me today. I went to a local beach and once I arrived I noted that the sand was way more black than I remembered, it is so full of iron that by just placing the sand scoop in the sand the internal magnet I have installed will fill up with iron dust and have the classic magnetic pattern that magnets do to dust. Anyhow here is the thing. I am still waiting on my PI machine, even though I believe that not even that can work with this type of sand, so I took my whites m6. Well needless to say that as soon as I turned it on, even at min sensitivity it would overload...
So I just wondered what would happen in wet sand... And I tried... The m6 was stable and silent at about 50% sensitivity, and no overloading, even if I couldn't find one thing, I ended up taking my wedding ring of my finger and placing it at about 4 inches under the sand, I could pick it up no problem.
Now I have just got one explanation to this wet sand vs. dry sand scenario, I believe that since there is such concentration of iron in the sand, the water makes it sink, living an iron free sand on the wet part of the beach, while the dry part keeps the iron superficial.
Maybe some one can confirm this (or not), but if it's like that than the only way to detect a black sand beach with a VLF detector would be working in the wet sand instead if the dry sand... Mainly the opposite of a normal beach ..

Comments are welcome....

 

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[Sir Gala Clad]

Nobyx: What you refer to as “strange behavior” is not strange if you look at what is happening specifically rather than try to fit it into a generalization.
Conditions are not only beach specific; conditions may vary on the same beach significantly within the day.

First let us look at the dry zone of the beach. You have identified a heavy concentration of iron in the dry sand by its blackish color and the fact that iron particles are sticking to your magnet. This is a ferrous coin/target situation where the iron in the sand is detected by a VLF detector as ferrous junk which can be discriminated / processed dependent on the capability of your detector.
As you have not encountered it before. It is most likely is a temporary condition which is not characteristic of your beach and can be spread by the wind, driven down by rain, or moved away tides / wave action. This appears to have already happened in the wet sand zone.

Dealing with wet sand at salt water beaches is a different challenge as you are dealing with conductivity which varies dependent on the salinity of the water. Increased salinity increases the return from the ground which is noise to the detector. In this situation you can get by by reducing the sensitivity of your detector. You may find that after heavy rains, you are able to detect with a single frequency VLF without having to reduce the sensitivity since the rain has diluted the salinity of the soil there is less of a return (noise) from the soil.