Prospecting Techniques; Identifying Target Signals - Minelab GP Extreme User Manual

THE MINELAB 'GP extreme'
www.minelab.com

PROSPECTING TECHNIQUES

The 'GP extreme' has superior ground balancing and it is possible to find quite large
objects near the surface in well-worked areas where other detectors have been unable to
cope with the high degree of mineralisation and / or salt. Therefore the user should dig all
target signals, even in previously detected areas.
For Maximum Gold Recovery
Keep the coil as close to the
ground as possible.
Listen very carefully - this is
more important than looking.
SLOW DOWN! Do not rush, take
your time.
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PROSPECTING TECHNIQUES
Very sudden or large changes in the mineralisation of an area may
produce a signal from the detector.
In the Victorian goldfields, a response may be received from a
concentration of orange/reddish dyke material or clay. In the loamy
conditions of Western Australia, a pocket of dark orange/reddish
colouration may produce a sudden signal change.
If detecting areas of extremely variable mineralisation, detecting with
the contours rather than across the changes will often stabilise the
effect.
In some ground (particularly heavily mineralised areas) the
operator may need to sweep the coil 1 or 2 cm above the ground.
This should give a more stable threshold and less ground noise.
Charcoal may sometimes produce signals, similar to a metallic
object, when close to the surface. Charcoal is usually created by
farmers burning off tree stumps or by bushfires.
When the charcoal under the surface is disturbed, the signal will
vanish.
If in doubt, scrape away some soil above the suspect signal; if the
signal gets stronger, it is likely to be a target. Dig it!

IDENTIFYING TARGET SIGNALS

Metallic targets will usually give a 'solid' sounding signal when the coil is swept across
the object from any direction. Ground noises usually give a broad uneven signal when
the coil is swept from different directions. A metallic target generally produces a short,
sharp and mostly symmetrical signal.
If you are not sure if the sound is ground noise or a target signal,
you need to investigate.
Scrape a shallow hole about 70-100mm deep over the suspected
target. Sweep the coil over the hole at the original ground level.
Do not dip the coil into the hole. If the signal has decreased in
volume or is less defined, it is probably ground noise.
If the signal remains the same or becomes louder, it is likely a
metallic target. If you are still not sure, make the hole deeper and
repeat the process. You may also notice that mineral noises are
often experienced from one direction only, on the return swing it is
no longer there.
A 'halo effect', which may be built up around a buried metal object,
makes the object appear to be larger to the detector than it actually
is. This will be reduced once the target is disturbed from its position
in the ground (e.g. a small object, detected at a substantial depth,
may be more difficult to detect once recovered from the ground. If
the object is reburied, the 'halo effect' will disappear)
HINT Do not try to eliminate what might appear to be a faint,
isolated ground noise by balancing the detector because you may
be 'balancing out' the target response from a deeply buried metallic
target.
THE MINELAB 'GP extreme'
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IDENTIFYING TARGET SIGNALS