Why a hoard test with modern coins is inaccurate

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{Why metal detecting hoard test with coins in a jar is inaccurate}

Why hoard tests with modern coins in a jar is inaccurate and don't present real search

Hoard tests with modern coins in a jar are inaccurate, misleading and do not present a real search scenario, because modern coins are more conductive than ancient coins which have been buried under the ground for a long period of time. The modern coins will be detected deeper.

Why are ancient coins less conductive?

Old coins have a patina
During the time spent under ground coins becomes corroded and oxidized from reacting to the soil elements and moisture. This cause a thin layer to form which is called a patina. The color can range from shades of green, brown, blue and purple. This layer reduces the ability for current to flow through the metal.

Uneven surface
Old coins were often struck by hand which would cause uneven thickness. Cracks would also form due to the rapid and uneven pressing method using a hammer, unlike modern coins which are made with a hydraulic press. Some coins were stuck cold which would make them less moldable than those which were heated first and they became susceptible to cracks. These uneven surfaces disrupt the eddy current flow, resulting in less conductivity.

Mixed with impure metals
Old coins were often mixed with impure, less conductive metals.

Nexus Metal Detectors

Nexus

{Analogue metal detector control functions with LED meter}

What does conductivity mean when metal detecting?

While out hunting you may wish to only dig out certain targets and avoid others. Metal detectors are provided with visual and sound indicators to show how conductive the target underground is that your metal detector is detecting.

The Foundation

Metal conductivity simply means how easy or difficult it is for electric current to flow through the metal.

Conductivity examples in regards to metal detecting

Low conductors

Generally small and thin items, such as tiny gold nuggets, small gold rings, thin gold chains, small hammered gold or silver coins and small Aluminium foil pieces and fragments.

Medium conductors

Medium to large gold jewelry.
Relics made of material such as lead, brass and smaller bronze artifacts.
US Zinc pennies and Nickel coins, smaller Euro coins

High conductors

RGB METER READINGS

Specific metals do not equal certain conductivity.

For example gold doesn't have a certain conductivity as a rule. A hammered gold coin may have low conductivity, where as a large chunky gold object may have high conductivity. This means meter readings will be different for these gold targets even though they are made of the same metal.

The Nexus RGB meter based on LED technology.

It provides a reliable visual discrimination analysis in:

All-Metal Mode
VCO Multi tone mode.

Non-Ferrous targets

Conductivity range indicated by each of the three basic LED colors:

Green
Only the lowest conductors.
Orange
indicates everything between medium conductors
such as most of the coins found by metal detectors both modern
and ancient.
Purple / White colour indicates mostly high conductors such as
thick Silver coins or large non-ferrous targets such as big
bronze/copper pots.

The RGB meter also indicates Iron targets in Blue color.

Relationship between conductivity and hoard hunting

Nexus Why hoard tests with modern coins in a jar are inaccurate and don't present real search

When performing a hoard test, users would often use modern coins in a jar. The reason this is incorrect is that modern coins are far more conductible than ancient coins and the signal strength when demonstrating with the modern coins will be much stronger than when out in real conditions searching for the ancient, valuable coin hoards.

Nexus Metal Detectors