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Page 34 The Minelab Eureka Gold

11.2 Clay Domes

A common occurrence in nugget-bearing country is soil mineralisation

commonly known as ‘clay domes’. These are regions of rather broad sound

which could be confused with the sound which would come from a large

deep nugget.

The following procedure will quickly establish whether or not the sound

comes from clay or a metal target:

a) Pinpoint the target as best you can.

b) Remove about 4 cm (1.5”) depth of soil from over the target response.

Dish the hole so that there are no sharp edges around the hole.

c) Sweep the coil across the target from a few directions, keeping the

coil as low as possible. Listen to the signal and note if it is:

— Any louder or more defined than before. By bringing the coil closer

to a metal target the signal should become louder.

— Note if the signal seems to come from one direction only

(a mineral signal will often come from one direction only, or at

least be less defined from the return sweep).

d) If you are still not sure, continue to dig deeper and again, note the

points above.

e) Be sure to dish the hole when digging to ensure there are no sharp

edges. Sweeping the coil across the sharp edge of a hole can cause

false spurious signals due to the change in distance between the

ground and the coil.

11.3 Charcoal

Charcoal can sound loud and rather like a metallic target when close to

the surface. Charcoal is usually created by farmers burning off tree stumps

or by bushfires. The growth is burnt below the ground level, so it is not

always obvious what the sounds are until you have actually dug up the

causes of these noises a few times. Again, experience will teach the

operator how to read the ground efficiently and gain understanding of the

detector’s response to the ground.

An indication of charcoal is that the sound seems very spread out and

becomes patchier as the ground is dug. Inexperienced operators should

continue to dig until the reason for the signal becomes clear.

Page 35 The Minelab Eureka Gold

11.4 Gold Lore

To have a good chance of detecting gold, it is necessary to search out

areas where ‘coarse gold’ is known to have been found, or other areas

where it is likely to occur. The term ‘coarse gold’ refers to gold ranging in

size from a grain of wheat to many grams, and in some cases many

ounces.

Many nugget-bearing areas are the result of broken-down gold reefs

containing quartz and ironstone. Experienced prospectors learn to

‘read the ground’ and look for tell-tale signs indicating potential

gold-bearing fields. It is a fascinating and exciting hobby to learn some of

these skills and apply them in your search for gold.

The modern metal detector has given today’s prospector enormous

advantages over the prospectors of old. The ground can be rapidly scanned

until a small piece of gold is found and then a study of the area made to

decide where other gold nuggets are likely to be located. It is then best to

make a systematic search of the area.

The main problem encountered while using metal detectors is the

presence of heavy concentrations of ironstone. This is particularly the case

in some of the richest known fields in Australia or the ‘black sands’ areas

of North America. It appears that gold nuggets and ironstone often go

together, and in fact many gold nuggets have ironstone embedded in them

or are encased in ironstone and others show strong ironstone

staining. Some of these fields have only been superficially worked by

detectors because of the interference caused by the ironstone. Usually

only the most persistent professional is prepared to spend the time and

energy necessary to cope with these conditions and then only partially.

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