HELP....Tech question on "Black Sands"

[Tony]

What component of "Black Sands" causes detectors problems?

Is it just Magnetite that is the problem.

I need to hunt an area that has black sand. I have sampled some of the material and under a very strong magnet NO particles are attracted to the magnet.

What else do I need to consider if there appears to be no magnetite?
There are black particles but I just don't know what they are or what properties they carry?

I know my Goldquest SS stands the best chance but the area is littered in symmetrical iron pieces.....

Reg...Eric...heeelllppppp !!
I have read all the threads on "black sand"...Magnetite/Maghemite/Hematite

Regards,
Tony.

 

[huntingthebay]

n/t

 

[huntingthebay]

n/t

 

[Eric Foster]

Hi Tony,

I have been to some beaches where there appears to be black sand. It is often about 10 - 12in down, but gives no signal on a PI detector. I think that the black colouration is caused by decaying organic matter in an anaerobic situation, rather than iron minerals.

Beaches that have genuine magnetic black sand are sometimes loaded with magnetite grains which do stick to a magnet, but are still undetectable on a PI. They play havoc with a VLF though, because it unbalances the coil circuit (DD or concentric).

Other beaches, derived from basaltic material in particular, will give a signal on a PI and, depending on the strength, may need a detector with ground balancing, or at least a DD coil. Here, the effect is causes by the presence of maghemite grains, as well as magnetite.

Eric.

 

[Tony]

Eric,

Thanks for the update.

It appears that the black material shouldn't be a problem as I'd like to run a VLF to overcome the iron target infestation.

I also noted that the material (took some home) will not deflect a compass needle so that's encouraging as well.

Have a great Christmas....hope it's not too cold in London as I'll be there next week

All the best,
Tony.