Halo effect in rock

Does anybody know if the halo effect in a solid rock formation is more or less than in dirt for the same sized piece of gold??

Regards
Daggs

Daggs, I am no expert, but here are my thoughts.

Basically it would depend on the type of rock and type of gold. If the so called halo from a nugget is like rust coming out of a bit of steel, then:

I would doubt if there is any halo around primary gold in quartz. It is essentially impermable and every bit of gold comes out very shiny with no oxidation.

In the case of a nugget in a cement or conglomerate, which is essentially alluvial dirt gone hard, it would depend if the halo had formed before the material the nugget was sitting in was turned to stone.

If it is secondary or supergene then presumably there has been gold in solution so it could I guess.

Personally, I don't really think there is a halo around gold. Rusty steel - definitely. Gold - it would take millenia to dissolve and then it would have to stay in the same spot all that time. If there is a halo it would be minute.

Regards
Stingray

Hi Stingray,
Thanks for your reply,
I have definitely seen the Halo effect a few times with targets that disappear when they have been removed from their resting place and are then difficult to find, (especially if they are small).

Here is an exert from the Minelab GPX5000 manual.
Halo Effect
After a metal object has remained undisturbed
in the soil for a considerable amount of time
a diffusion occurs around the object. This
has the effect of the object appearing to the
detector to be a larger size. page 88
and
A ‘halo effect’, which may be built up around a buried metal
object, makes the object appear to be larger to the detector
than it actually is. This will be reduced once the target is
disturbed from its position in the ground (e.g. a small object,
detected at a substantial depth, may be more difficult to
detect once disturbed from the ground and lying in the
loose dirt. page 81

I am really trying to determine if a lump of gold in a rock will have the same sound (loudness & pitch ) as a similar sized lump (nugget) in dirt.

Just curious if anybody has heard and removed nuggets / specimens from solid rock buried at depth.

Regards
Daggs

Hard question to answer really, its well known that a nugget in the ground does in fact give a better signal when undisturbed due to what commonly called the halo effect, once the nugget is removed from its resting place it can then sometimes be hard to locate in the loose dug out soil if its quite small, we have all found small nuggets in others people's dig holes and that is probably why.

Nuggets that I have broken from rock, say like conglomerate don't always give a very good signal at first even though some have been in the 10 to 20 gram range, so I think maybe the gold is masked by the mineralisation that is in the surrounding conglomerate mixture, once out they give a normal response.

Gold that is contained in quartz or in specimen nuggets often give a good signal, but I don't think you could call it a halo effect like in the nugget in the dirt sense, often the surrounding quartz around the position of the larger lump will have stringers and very small particles of gold that's not always visible to the naked eye, these additional particles will probably help depending on the concentration of them to contribute to the overall signal effect.

Hope this makes sense

au-prospector

Thanks for your reply au,
I like your explanation.
Hopefully I will know the answer to my own question when I retrieve the signal I have been chasing in rock very soon. I'll let all know when it comes out.

Daggs