Quote:
Originally Posted by danhughes
Hi, JP. I've heard from a lot of people after I posted that show, many of them taking issue with the whole concept of the halo effect.
Perhaps the term "halo effect" is a poor name, but I've experienced the phenomenon many times.
I used a multitude of sources, but here's the best article I found on the subject:
http://www.njminerals.org/metaldetec...aloeffect.html
Best,
---Dan |
There is one important error in the halo effect reference - copper is not a noble metal.
There is also a photo of a silver coin with a black coating. This is clearly the result of tarnishing. That is, the result of a hydrogen sulphide reaction with the silver surface. This is the same reason you have to polish your silverware to restore the shine.
Personally I have only experienced the halo effect on a few occasions, when recovering deeply buried copper coins, but never with silver coins. In cases of extreme depth for single coins, the real reason is usually that the coin was lodged in the side wall of the hole, and falls out during the excavation.