How My Metal Detector Works In Mineralized Soil A test of the Garrett GTI 2500 in very mineralized soil

The Parks Service in my home town uses a sand for children's play areas that has a lot of iron in it, which makes it mineralized. How mineralized? Try this:

I took a cup of dry soil from my back yard, which doesn't bother the detector at all, and a cup from a playground, which causes the detector to scream an overload warning whenever the coil gets closer than 1". Using a strong magnet, I collected all the iron I could from each cup. The small pile of iron on the left in the picture is the amount I collected from my yard: less than 1 gram. The pile on the right is from the cup of playground sand: over 25 grams! (Color differences are the result of merging two different photos.) That means that the playground sand has almost as much iron in it as the weight of a silver dollar... in each and every cup. No wonder my GTI 2500 hates it.

The real question is: How much does this mineralization effect the detector's ability to find targets? I spent a morning burying quarters to find out. The answer is that it reduces a Garrett GTI 2500's ability to spot a newly-buried clad quarter from a maximum of 9" inch clean soil to only 6" in heavily mineralized soil. The Target Imaging function is reduced from 5" to 3.5". That's about 33-percent in both cases. Is this good or bad? Until I get my hands on some other detectors and subject them to the same tests, I won't know.

Adjusting the sensitivity, manual ground balance and frequency did not prevent the detector fro sounding an over load alarm when the coil was closer than 1" to the soil. Raising the coil to 1 and 1/2" prevented this and enabled the detector to function normally.

An interesting and potentially valuable result from this test is that it suggests that a formula could be developed for a standard level of soil mineralization for testing detectors.

 
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