What is the best way to find a spot of mineralized ground

[Unregistered]

Hello people,

I have a question and hope some of you can help me with it.

Over a hundred years ago a bronze age hoard of bronze axes and spearheads was found in the Netherlands. The precise findspot is now only know by a couple of hundred yards or so. The original reports mention a layer of green copper oxide under the bronze artifacts. This copper-oxide must have accumulated over 3000 years as a sort of powdery substance imbeded in the soil.

I want to pinpoint exactly the spot where this hoard was found. The objects themselves have already been removed but the copper-oxide under them must still be there. In order to locate the copper-oxide I want to use a metal detector that I will rent or buy.

My guess is that the copper-oxide will locally increase the conductivity of the soil. Whereas most treausurehunters want to cancel out mineralized ground, I am actually looking for the ground effect it causes.

This is what I have learned so far:

Ground effect can be caused by either magnetism (Iron minerals) or conductivity (metal salts like copper-oxide, or salt water)

In order to get a lot of ground effect I should use a big concentric coil

I should use a detector with a higher frequency (the lower frequencies react better on ground effects caused by iron minerals).

But now I wonder in what operation mode to use the detector. My guess is that the best way to go about is to manually fine tune the ground balance of the detector on lightly to non-mineralized soil. Then search in an all metal, non-motion (threshold-tone) mode. When the coil comes over the spot containing the copper-oxide the threshold tone should increase. The detector should not use auto-ground-balance and auto-retune because then the detector will retune when I reach the mineralized spot. Perhaps a tesoro bandido would do the job?

But I could be mistaken here. Perhaps I should buy the cheapest (2-filter) detector available and sweep the coil like a maniac in a motion mode with low disc setting. Can someone help me out on this one please.

Sorry for my bad English. It's not my native language.

Thanks, Marc

[Max]

Hello people,

I have a question and hope some of you can help me with it.

Over a hundred years ago a bronze age hoard of bronze axes and spearheads was found in the Netherlands. The precise findspot is now only know by a couple of hundred yards or so. The original reports mention a layer of green copper oxide under the bronze artifacts. This copper-oxide must have accumulated over 3000 years as a sort of powdery substance imbeded in the soil.

I want to pinpoint exactly the spot where this hoard was found. The objects themselves have already been removed but the copper-oxide under them must still be there. In order to locate the copper-oxide I want to use a metal detector that I will rent or buy.

My guess is that the copper-oxide will locally increase the conductivity of the soil. Whereas most treausurehunters want to cancel out mineralized ground, I am actually looking for the ground effect it causes.

This is what I have learned so far:

Ground effect can be caused by either magnetism (Iron minerals) or conductivity (metal salts like copper-oxide, or salt water)

In order to get a lot of ground effect I should use a big concentric coil

I should use a detector with a higher frequency (the lower frequencies react better on ground effects caused by iron minerals).

But now I wonder in what operation mode to use the detector. My guess is that the best way to go about is to manually fine tune the ground balance of the detector on lightly to non-mineralized soil. Then search in an all metal, non-motion (threshold-tone) mode. When the coil comes over the spot containing the copper-oxide the threshold tone should increase. The detector should not use auto-ground-balance and auto-retune because then the detector will retune when I reach the mineralized spot. Perhaps a tesoro bandido would do the job?

But I could be mistaken here. Perhaps I should buy the cheapest (2-filter) detector available and sweep the coil like a maniac in a motion mode with low disc setting. Can someone help me out on this one please.

Sorry for my bad English. It's not my native language.

Thanks, Marc

Hi,
what's the depth of stuff ? Do you know the depth and extension of supposed copper/bronze oxide layer ?

I think it's not so easy... but maybe not impossible task: only way to know is try.

If is like e.g. 10cm^2 thing and at say 20cm depth and soil was not disturbed anymore then there is possibility you can pinpoint exact place.

You can use a vlf detector with manual GEB control like bandidoII and thus nulling on ground in that area in a place where you know there isn't the spot position... then you'll search for sharp anomaly on that soil using detector in disc mode.

Actually oxides aren't conductive so there's no more conduction in soil due to that only... but chemical interactions could happen there and also you can detect slight diamagnetic behaviour by sensitive VLF machine.

I suggest you use a very senstive VLF only... not PI or other stuff cause you need detecting diamagnetic anomaly there... so better disc out iron and iron salts as possible (using disc mode).
An original bandidoII will maybe not find that spot... cause you know is not so sensitive machine but maybe an optimized one could do... I suggest you find the most sensitive VLF you can buy or rent and without auto ground balancing... just manual setting.

Other interesting try will be with e.g. cesium-magnetometer... you know... a large diamagnetic spot will reduce local magnetic field and thus be revealed by a map of levels ... but requires , of course, a larger budget and lot of measures and time.

Kind regards,
Max

[Unregistered]

Thanks for your reply Max,

The mineralized spot should measure about 1 square meter. A magnetometer is way out of my budget. I think I will have to settle for the VLF-detector option.

I never heard of diamagnetism before, and now I realize that things aren't that simple as I thought. I will have to do some more research on the subject.

I ordered this book at the library: Thompson, R. & F. Oldfield, 1986. Environmental Magnetism, London. Besides that I have ordered 1KG of copper-carbonate at the local arts-shope (potters use it to get a green glaze). I first want to do some experimenting with various metal detectors and that slightly toxic green stuff before I hit the field (detector settings, wet versus dry soil etc.).

Marc

[Reg]

Hi Marc,

You have the right idea of experimenting to determine what you can or can't do with a detector.

Now, with that said, I highly doubt you will be able to obtain any logical signal from the copper oxide in the ground or the copper carbonate if you pour it on the ground also.

I suspect the axe heads were found because of their metallic content, or they could have been found by looking for distinct anomalies in the ground signal. A hoard of bronze axes and spear heads would require they be made and logically, the making of the axe heads and spears would have occurred reasonably close to the storage location. Since a kiln or crude furnace type device would have been used to heat the ores sufficiently to melt out the copper, then such heat would have altered the iron oxide in the brick and mud used in the kiln shell or the surrounding ground. This intense heat would have dramatically altered just how the brick and mud would respond by changing the iron oxide characteristics.

A PI or a VLF could be used for this purpose, which would be to look for a distinct change in the ground signal. In fact, I think this ability is one of the main reasons so much work was initially done on developing PI's to begin with.

Anyway, once you get a chance to experiment, please let us know what you find out.

Reg