There have been a number of forum posts, questions and comments concerning the ‘halo effect’ that many encounter while detecting. Most explanations are great but sometimes too complicated.
Let’s look at what the halo is and how it affects you while detecting. In the simplest form the halo is nothing more than the oxidisation of a target. Anything buried in the ground that will rot, corrode, tarnish or leach can cause a halo effect.
The halo can be very frustrating to detectorists due to the fact that what seems to be a good target can simply disappear.
Let’s look at it from a nugget hunter’s perspective. There is no such thing as pure gold in nature. Gold is generally associated with a number of other metals including copper and silver. Both of these metals will oxidize and can send a larger conductive signal back to the detector. Now the actual gold target could be very small but the halo signal created by the other metals could really sound off making a hunter think there was a very big signal in the ground.
Once the detectorist starts to dig the signal the halo will collapse, because the electromagnetic field around the target has been broken. At this point the small gold signal could sound just like ground minerals. Many detectorist thinking there is nothing there will call it a ghost and move on. I have seen too many people walk away at this point leaving a good target in the ground.
You have put a lot of energy into the ground with your detector and your energy and effort into digging a hole. If this happens to you, before you walk away, re ground balance your detector away from the hole and check it again. Get it out of your head that you are listening for a bigger signal like you first heard but concentrate on listening for a tiny bump in the threshold. That bump you hear will be your real target. It is really a phenomenon of physics that turns into a mental miss for almost all of us. You’re listening for that big signal that simply no longer exists.