Metal detector & pyrite...and eventually gold

[ssr60]

Hello !

What kind of metal detector is good at finding iron pyrites ( FeS 2 ) and others pyrite targets ?

Which one is a better high or low frequency search coil ? ( iron pyrites ja others pyrite targets )

Thanks you everyone !

[Eric Foster]

Hello,

Iron Pyrites is a difficult metal to detect because of its low electric conductivity. One detector that I know works is the Fisher Goldbug 2. I have some pyrite cubes from Northern Spain and the GB2 will detect these OK provided more than 1/2in cube. You definitely need a high frequency detector and the GB2 runs at 70kHz.

Eric.

[El Cooter]

He would know!!

[nuggetshooter323]

I have a Lobo Super Traq and it works at 17.5 khz, and it doesn't utter a peep with pyrite, which is just fine with me. Now I have a Falcon MD20 probe, and it works at 300 khz, and it also doesn't utter a peep with pyrite. Why does the GB2 sound off at 70 khz with pyrite?

[Jim Hemmingway]

Hello SSR60,

I checked out two iron pyrite (iron sulphide) samples in both true all metal mode, and in zero discriminate mode on my Spectrum XLT (frequency somewhere around 6.6 kHz..I can't remember exactly, but it"s close enough...it's low frequency, coil size nine and one half inches). The auto track was turned off, and the detector was manually ground balanced to about minus 93 VDI (-93) out in my patio....with the samples laid on the frozen ground (that ground balance implies pretty tough mineral background ie close to black sand). Disc Sens @ 64 out of 80, All Metal Sens @ 48 out of 60....modest sensitivities.
(a) the first sample, about two inches long by an inch and a bit in diameter/width gave no reading at all. Nothin'.
(b) the second sample, about two and a half inches by two inches in diameter/width gave a reading that fluctuated between minus two (-2) and plus four (+4) VDI, in both modes (entering the lower foil range).

In either mode the audio response was quite weak, the sample could only be detected approx. two inches from the coil. In discriminate mode, the audio signal was broken (not diggable), while the all metal signal was smooth and clear.
The above VDI range is about what you would expect from low grade silver ore (with bits of native silver showing from low conductive arsenic-cobaltite mix in calcite), but the difference is that same size low grade ore gave off a much more powerful signal and could be detected out to about 10 inches. Thus, a good sized sample of pyrite can be detected with a lower frequency detector, but it's a real low power conductive, implying you must get the coil close to it in order to detect it. Fortunately, some pyrite dumps offer good pickings right on the surface. If you want to hunt this stuff, take Eric's advice above. Hope this helps.

Follow up: A couple of interesting bench test points (a) as the XLT ground balance was decreased from a black sand level to lightly mineralized ground conditions, the pyrite response in all metal gradually diminished to a point where it no longer responded with an audio signal (b) using the Goldstinger, operating @ 15kHz, coil size @ 8 inches, all metal mode @ about 80% sensitivity, both pyrite samples were easily detected, the larger piece out to three and one-half inches easy. It did not matter whether the ground balance was set to black sand, or reduced to light mineralization, the response was pretty much the same throughout the entire span; a slight diminishing of signal strength as salt ground balance was approached (c) the overall signal strength was considerably stronger with the Goldstinger compared to the lower frequency XLT.
That's it I guess, you made me curious too...so long...Jim.

[UncleVinnys]

I have a Lobo Super Traq and it works at 17.5 khz, and it doesn't utter a peep with pyrite, which is just fine with me. Now I have a Falcon MD20 probe, and it works at 300 khz, and it also doesn't utter a peep with pyrite. Why does the GB2 sound off at 70 khz with pyrite?

Greetings . . . I just got the Falcon MD20 too, and was VERY IMPRESSED at its
super sensitivity. I tune it to just under oscillating, and I swear you can pick up
the earth's magnetic field by twirling that thing around !!! . . .
Anyway, I'm wondering how you use it, how it is used in conjunction with the
detector or by itself??

[nuggetshooter323]

It does pick up earthsmagnetic field, also, you can't hold samples in the palm of your hand because it will pick up the iron in your blood. I use my MD20 a couple of different ways. First, just like a regular probe with my Lobo Super Traq. It's not as handy as my vibraprobe as a belt stored probe, but I will not go into gold country without my MD20. The other way I use it is I plug in the optional headphones, and install the optional extender tubes on the probe, and walk up wet or dry stream beds and probe the cracks and crevasse's.

I have a Lobo Super Traq and it works at 17.5 khz, and it doesn't utter a peep with pyrite, which is just fine with me. Now I have a Falcon MD20 probe, and it works at 300 khz, and it also doesn't utter a peep with pyrite. Why does the GB2 sound off at 70 khz with pyrite?

Greetings . . . I just got the Falcon MD20 too, and was VERY IMPRESSED at its
super sensitivity. I tune it to just under oscillating, and I swear you can pick up
the earth's magnetic field by twirling that thing around !!! . . .
Anyway, I'm wondering how you use it, how it is used in conjunction with the
detector or by itself??

[ssr60]

Hello !

What to find a better iron pyrite (iron sulphide) PI or VLF metal detector ?

Thanks you everyone !

[Jim Hemmingway]

Hi SSR60,

It's been a year since you last posted on this topic. I presume you have not purchased a suitable detector, and I think you should consider that option carefully. I don't know about PI's ability to find this type of target, as I have not tried one.

To place this subject into perspective, trying to detect a dollar size piece of iron pyrite is about equivalent to locating a gold nugget sized between one and two grains or so.

A VLF unit must be highly sensitive to very low conductives like iron pyrite. That means a nugget hunting designed unit, and the highest frequency would be best overall. A GoldbugII or GMT will give the best performance to sensing low conductives.

I have tested all three of my prospecting units that range in operating frequency between 13 and 15 kHz... on a dollar size chunk of pyrite in the air here (the ground is frozen). All three units will sound off at roughly3 1/2" to 4", with a "diggable" signal at 3" or less depending on the unit. That's with the ground balance set to an equivalent of about 80ish (to simulate decently higher mineral ground) on MXT for all units and using all-metal motion mode. Non-motion all-metal mode (if available on the unit) can get an inch or so more, depending on the unit.

Those are air tests, I doubt you'd get much more than half that in higher mineral ground. I suggest that if you are intent on using a metal detector to search for pyrite, borrow a suitable unit, or rent a unit and try it out first.

Here in Ontario, we have abandoned pyrite mines especially in the eastern townships. You can walk into areas where the ground literally glitters with pyrite particles and larger pieces are often located just below the surface by common rockhounding methods ie pick, shovel and screens. If your research indicates such opportunity exists in your area, I would recommend you try this approach prior to buying a detector. Good luck and HH,

Jim.

[Yellow Hammer]

Hey Jim,

About the PI detector and pyrite. I have never picked up pyrite on my coil and always hunt in all metal. One day while digging a nugget I did find a nice nugget of pyrite but it was not what set the coil off that would have been the 1/4 oz nugget. Even waving the pyrite nugget in front of the coil there was nothing. Hope this helps about using a PI.

[Jim Hemmingway]

Thanks for adding your comments Yellow Hammer. I thought as much too.

You know, generally VLF units pretty much ignore pyrite unless set-up in a benchtest. I felt he should have that questionable information just to be complete, but I don't see metal detecting for pyrite as a good idea. My 2 cents worth is to stick with basic rockhounding tools...shovel, pick, screen and bucket.

I have an unusual question about PI units that you may have run across. I was in an area this past autumn that was littered with pyrrhotite. Its a low conductive iron sulfide that blocs VLF signals and makes some spots impossible to hunt. Do you have any idea if your PI unit will see through this stuff? Or does it respond with a signal? Take care,

Jim.

[Yellow Hammer]

Yes you will get an audio signal from the pyrrhotite but the PI will punch below it and the tone will be different and light. Even with the PI it will be frustrating as hell.

[Jim Hemmingway]

Yellow Hammer,

Thanks for letting me know. I was afraid that would be the answer because it is a (low) conductive substance. Take care,

Jim.