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Fisher Impulse AQ And Hot Rocks


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Me too.  😕 I'm hoping when it does come out that it does not pick up these rocks. They read #1 on the Equinox - right where the small gold and chains read. I would be willing to pay postage and send some of them to Fisher to make sure they are invisible to the Impulse AQ

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Just Do It!  Couldn't hurt.  GaryC/Oregon Coast

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17 hours ago, schoolofhardNox said:

Me too.  😕 I'm hoping when it does come out that it does not pick up these rocks. They read #1 on the Equinox - right where the small gold and chains read. I would be willing to pay postage and send some of them to Fisher to make sure they are invisible to the Impulse AQ

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Years ago I sent a box of coal waste dirt to Dave at 1st Texas for analysis.  Yes, they did test and sent a length reply as with what I could do when adjusting my F75 to hunt the areas.  

What exactly are they and where are they native.

Wonder how the TDI would react.

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9 hours ago, Mark Gillespie said:

Years ago I sent a box of coal waste dirt to Dave at 1st Texas for analysis.  Yes, they did test and sent a length reply as with what I could do when adjusting my F75 to hunt the areas.  

What exactly are they and where are they native.

Wonder how the TDI would react.

I always wondered if they actually care when you send them something like that. I may e mail them first instead of just sending them a box. Anyone have a contact person there? Mark, those rocks are at Rhode Island beaches as well as some Connecticut beaches. Probably MA and NH as well, I'm thinking. I'm not sure exactly what they are, but I'm thinking they are have a higher concentration of minerals and probably are magnetite. Just a guess. There are a lot of other black rocks that look identical, but do not read on the Equinox., so it makes it tough to detect in the rocks. The Garrett carrot also pick them up.

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21 hours ago, schoolofhardNox said:

There are a lot of other black rocks that look identical, but do not read on the Equinox., so it makes it tough to detect in the rocks. The Garrett carrot also pick them up.

Did you test to see if they are magnetic?  If not, graphite content is a candidate.  My White's TDI (locked at 10 microsecond delay) does not detect a very large graphite rock that my sister found in California, but both the Garrett Carrot and Fisher Gold Bug do.  The Gold Bug gives a TID of 40, which is right at the nominal ferrous/non-ferrous boundary.  That seems consistent with what you are getting with the Equinox.

 

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Do they seem unusually light? Some of them look odd, more like water worn coke or cinder perhaps than natural rocks. Any rocks with high graphite content can be an issue as GB noted as they read non-ferrous.

Since they read so low the Impulse will likely ignore them in disc mode since that is focused more on ring range targets. In non-disc mode advancing the pulse delay should eliminate them.

I know Dave Johnson has an extensive hot rock collection but not sure if he is adding to it anymore.

Advanced Nugget Hunting with the Fisher Gold Bug Metal Detector by Pieter Heydelaar and David Johnson. This out-of-print book is a good basic text on nugget detecting. Although it uses the original Fisher Gold Bug as an example the information applies to most nugget detectors. Part 2 by David Johnson is an excellent primer on hot rocks.

fisher-impulse-aq-metal-detector-prototype.jpg
Fisher Impulse AQ prototype

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19 hours ago, GB_Amateur said:

Did you test to see if they are magnetic?  If not, graphite content is a candidate.  My White's TDI (locked at 10 microsecond delay) does not detect a very large graphite rock that my sister found in California, but both the Garrett Carrot and Fisher Gold Bug do.  The Gold Bug gives a TID of 40, which is right at the nominal ferrous/non-ferrous boundary.  That seems consistent with what you are getting with the Equinox.

 

I tried it with a regular magnet and they do not respond. I will get a hard drive magnet and see if I get a slight response or not. Hitting on the same numbers that the small gold hits on, makes it hard to decide to dig or not. I dug about a dozen of them and gave up for a while. When I decided to start digging them again I eventually pulled up that 14K small earring. I wonder how many I may have missed???

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21 hours ago, Steve Herschbach said:

Do they seem unusually light? Some of them look odd, more like water worn coke or cinder perhaps than natural rocks. Any rocks with high graphite content can be an issue as GB noted as they read non-ferrous.

Since they read so low the Impulse will likely ignore them in disc mode since that is focused more on ring range targets. In non-disc mode advancing the pulse delay should eliminate them.

I know Dave Johnson has an extensive hot rock collection but not sure if he is adding to it anymore.

Advanced Nugget Hunting with the Fisher Gold Bug Metal Detector by Pieter Heydelaar and David Johnson. This out-of-print book is a good basic text on nugget detecting. Although it uses the original Fisher Gold Bug as an example the information applies to most nugget detectors. Part 2 by David Johnson is an excellent primer on hot rocks.

Steve, All the rocks pictured are the normal weight and not light . They look like the basalt we have in this region. Reading up on basalt it can have pyroxene minerals which can have iron and magnesium as components. Maybe all the black rocks are basically the same here except for the higher contents of metals present?? Just my guess on it. They may have graphite in them too, as some have that shiny silver look mixed in them. I'm hoping you are correct on the impulse ignoring them. That would be a huge plus for me.  I'm pretty sure the GPX ignores them, just not the Equinox. I'll look up that book. Thanks

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Hi,

hot rocks / / light
no particular problem
most of them are from basalt magma

heavy stones with high density
from granitic magma / can cause problems

of all of my  beach tests / last two years
only one still poses noise problems
it is crossed by a strong vein of granite magma ...

we tested dozens of hot rock
from all over the world
and several volcanic beaches
more than 95% are eliminated / without losing gold
with impulse AQ


sent some samples to Carl Morland
First Texas Products 1120 Alza Dr / El Paso / TX 79907
specifying to test on impulse AQ
he will do it without problem

I want to test them / but the shipping costs will be expensive.. :)

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2 hours ago, LE.JAG said:

heavy stones with high density
from granitic magma / can cause problems

Interesting and not surprising at all. My number one hot rock issue in many areas using Minelab detectors is with rhyolite, which is the finer grained extrusive equivalent of granite. There are some versions in California that read as a nice positive gold type target with the GPZ 7000. Luckily they are usually large and on or near surface and revealed with a kick. The signal they produce drops off rapidly with distance. But every once in awhile I get a very nice mellow gold nugget signal only to dig a few inches and find one of these that are softball size or larger.

In the Nevada desert I run into a version of this that are very odd in that when excavated they are often shattered, like they exploded into shards in place in the ground. Those are exceptionally "hot" and can produce signals to greater depths than the California version, and smaller pieces on the surface produce non-ferrous gold signals that mess with the high frequency VLF detectors.

The main problem with these rocks is they stand out as dramatically different than the ground they are in. I can ground balance on them and get them to go away, but then the ground is way off balance. Some detectors are better able to find a halfway point in the ground balance that can mellow both the ground and these rocks but typically you have to lower the gain/sensitivity a lot to enable this. The new XGB ground balance on the Goldmaster 24K actually does seem to handle these better than other VLF detectors I have used.

I do intend on getting the Impulse AQ and I also plan on trying it for more than beach detecting. I know that is its intended use but it may also have oddball applications for places with larger gold nuggets and lots of ferrous trash. I love trying something that actually is really new as experimenting with stuff like that is half the fun for me. Too many detectors these days are just the same old same old I have used for 20 years with slight variations. Truly new detectors only seem to come along once a decade, though things are heating up now it seems.

 

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