[J_Player]

Originally Posted by Ivconic

Coin presents very small "mass" to more significantly disturb surrounding soil. No matter how long it will lay in it.

Originally Posted by Ivconic

Surrounding soil will "suck" all the "radiations" from coin and dilute it easilly.

Hi Ivconic,
You are right about small mass of the coin. But what has been discovered is there are metal ions that move away from the coin in all directions and become disolved in the soil. There is no defined diameter because the concentration diminishes logarithmically. (We can say that there is a good halo at a 10 cm radius, even though it extends farther in weaker amounts). This raduis sphere is tranformed into a vertical column that moves slowly upward due to the capillary actions of the rain cycles. The ions continue to populate this column until the final 10-30 cm of the surface.

Thus, the halo area is many hundreds of times larger than the coin when measured by volume. Suppose a coin was buried 40 cm deep, and had a cylindrical column of ions dissolved in soil that approximated 10 cm radius with 25 cm height. --- The volume of this ion column is nearly 8 liters. How many coins would fit in 8 liters?

To be fair, the halo area of ionized soil may not be as strong as the coin for showing eddy currents in a metal detector, but it contributes sometimes to show a signal nearly twice as strong. What is more important is the electric field effects. The atmospheric current leaking between the earth and atmosphere will tend to favor areas of the ground that are more conductive, and transfer charges more easily. This anomaly made of ions, while having lesser mass than the coin, can have a large influence on the voltage gradient above the halo ground. Maybe large enough to measure. But as you say, there are many other interfering noises that make this hard to find. Some of the best conditions are:

1. Away from civilization - power lines, radio broadcasts, etc.
2. Between the hours of 10:00am and 2:00pm (may vary ins different countries)
3. Low relative humidity
4. The soil must contain chemicals that dissolve the metal. Otherwise there will be no ions or halo. For gold, this means there must be some gold-digesting bacteria that can corrode the metal by secreting cyanide and sulfur complexes. These bacteria have been found up to 5000 feet deep in gold mines, as well as near the surface.
5. Damp soil - preferably drying after a wet spell.
6. Long time buried metal. it takes some time depending on the metal.
7. Copper, lead, iron and zinc are known to dissolve a high concentration of ions in some soils. Most common metals are good for creating a halo. Poor metals that take longer are gold, stainless steel, platinum, palladium, etc.

Best wishes,
J_P