Prospecting Tips; Mineralisation And Hot Rocks - Minelab Eureka Gold Instruction Manual

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11.

Prospecting Tips

It will take time and practice to learn how to recognise which signal to
pay attention to or to ignore.
The Eureka Gold is particularly good at minimising 'ground noises', and
this is the reason for the exceptional depth capability. However, even with
this detector some ground noises may occur, particularly in heavily
mineralised ground.
11.1

Mineralisation and Hot Rocks

Typically, heavily mineralised ground can make a detector respond with an
indication that there may be a target reasonably deep beneath the surface.
The sound is normally rather broad and not very loud, but occasionally it
may be crisp and reasonably sharp. Other noises which most affect
detectors are caused by 'hot rocks'. These are rocks rich in minerals
which can produce very strong audio signals. With the strong ones, some
detectors have problems in tuning them out, but with the Eureka Gold signals
from 'hot rocks' are not as great a problem.
If you find a signal which may be due to mineralisation, but is 'positive'
enough to make you suspect a deep target, pass the coil in a circular path
around the area, without passing directly over the target. After two or three
rotations, pass the coil directly over the centre and listen to the
'positiveness' of the signal. Repeat this procedure but this time sweep at
right angles to the previous pass. If both passes result in a significant
positive response, then dig!
It is possible for gold nuggets to be entirely encased in rocks, so thorough
checking is necessary to ensure no gold is missed. Breaking rocks in two,
then passing each section of the rock across coil, one after the other, will
determine which piece contains the gold.
Sometimes negative 'hot rocks' or ground 'holes' are encountered. In this
case the sound from the detector is reduced as it passes over the rock or
'hole'. Nevertheless, the detector, on recovering from this loss of sound,
can give an audible signal which, to the beginner, may be confused with
the sound of a target. Experience will soon enable the operator to
recognise this characteristic sound which is in fact quite different from a
target. Setting the Signal switch to Fine may reduce this problem.
The Minelab Eureka Gold