HOT ROCKS - COLD ROCKS

[Eric Foster]

Hi Prospector Al and Vlad,

You may have seen this, but it is a good site for comparing the conductivity of metals.

http://www.eddy-current.com/condres.htm

Eric.

 

[Anonymous]

n/t

 

[Prospector Al]

Not enough ampere-turns to do the job. There are methods that work however: Paleomagnetic investigators "clean" rocks by subjecting them
to specific temperatures and remove the remanent magnetism in "layers". The results have shown that the polarity of the earth's field has "flipped" a number of times in the past. The north pole is
moving at an acceleratd pace at this time, so we may experience another such event in our life time...

All this is interesting but has little bearing on metal detecting. We need a method to tame these "anomalous rocks" where lie in the ground--a method that does not require a lot of energy. Else, we have to find a way to effectively discriminate againsts them.

The problem is that the time constants exhibited by these rock fall into the same range as gold nuggets. The signals generated by the magnetic and conductive properties of a target are antagonistic--that is to say, they have opposite signs and what the detector sees is the difference between their magnitudes. For ordinary ferrous targets, the magnetic component of the signal predominates, which makes differentiation easy.

Hot rocks, on the other hand, may exhibit a strong resistive signal and a small reactive signal, making the discrimination much more difficult.

I looked at the list of conductivities that Eric posted: I't good for the highly conductive targets, but the poor conductors are off the chart...

P. Al

 

[Anonymous]

n/t

 

[Anonymous]

They do not say-do you have any idea where 10k and 14k gold would read?