Knowing how iron effects the detection depth of a metal detector and in some cases iron masking can completely hide buried metal targets from detection I have a question about cache hunting. Now a little more information is in order.
Earlier this year I was removing old fence post and decided to bury a small cache of zinc pennies that I had found over the past years that were damaged to much for the bank to take. I used a plastic container that measured 4" in diameter by 6" long. I filled the container with pennies and buried it at a measured depth of 22". I took my detector, setup up as usual and began to sweep across the hole where I had buried the container of pennies. Nothing but a very low iron grunt sound and a VDI of iron came from my machine. Not being pleased with the results I dug up the pennies carefully checking the dirt for any iron and found one old rusted nail "4" long" about 15" deep right on top of the pennies. Okay bear with me here. I buried the pennies again while rechecking the dirt again for any iron. After finishing, I checked the hole with my machine and again only a low iron grunt. Well I dug the pennies up again, checking each handful of dirt again, nothing. This time I buried the container at exactly 12" from the top of the ground. I turned on my machine and still only a low iron grunt.
Now all that said, if a person was hunting for a buried cache of old coins what would be the best approach?
Turning the sensitivity up did not help.
Reducing the discrimination to zero did not help.
Running in all metal did not help.
What strategy would a person use in this situation?

I would guess, back in the day of fence post banks, they used mason jars or ball jars that had a tin lid or a wire snap. My detector sounds off on those lids as a high tone and pretty deep also.

Hmmmmmmmmmmm. Start by doing an air-test.....and see what the cache ID's as....and at different ranges. This may start to determine 'ground conditions'.

Update: I took my propointer and checked the area all around the buried cache of pennies and found some sort of metal targets (not dug up yet) buried close to the hole. Hope to do some digging around the area tonight. Very sure there will be something to report later. Still searching and learning.

A cache of zinc pennies should ID as a square pull-tab.....or higher.

A 4" plastic tub of CORRODED zinc cents in a freshly dug hole at 22"? You should not hear anything at all.

A 4" plastic tub of corroded zincs in a freshly dug hole at 12"? You might pick up something if the top of the container is within 6" of the ground, but doubtful if you have moderate or higher mineralization. The freshly dug hole will mask it. You aren't detecting a tub of zincs, you are detecting one of the zincs.

But....a plastic tub full of corroded zincs long buried at 12" where moisture and time have fused the zincs together into one big mass and the disturbed ground has melded back into the surroundings...you might pick something up. No telling what it would read as on the detector though as you are talking zinc. Zinc dissolves.

If you are doing a cache test, probably be better to use something that doesn't dissolve and prepare to allow some time for aging.

HH
Mike

Why 22 inches well I would think you are trying to say it is a big target and it should be deep. You might want to try the new mode on the LTD and set it up and see if you get a click or two...now if it was in a coffee can or mason jar you might get a peep if the soil is right.

LowBoY

[detectorstuff.com]

Like Tom says, how do you know what you are missing if you don't even know it exists.