Trinity AU....question


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Hi:

Ive talked with you in the past on the PH but figured I would post this in the forum as others may benefit.

Im using the GB Pro and have a tough time with heavy pockets of black sand. It seems to overload the detector.

The area im hunting in is very high in black sand and blanks out a target put in the soil. How would you overcome this?

Thanks

Tom H

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Gosh, ol' dutch john here. Let me chime in with my 2-cents. Magnetite, an iron oxide (Fe3O4) is found with other ferromagnesian members that makes up what is known as black sand.

It is the magnetite content in the black sand, about one to-two-percent, that causes a VLF detector to overload. (While the Pulses ignore magnetite and therefore are popular in Arizona).

Unfortunately, in Arizona magnetite, a member of the spinel group is a common and widespread accessory mineral. It is found nearly everywhere... abundent in metamorphic sedimentary and plutonic granites, abundant in metamorphosed limestone and other contact metamorphic (skarn) contacts. In volcanic rocks, in pegmatites.... WOW...

The best way to hunt for placer gold is to seek out mining districts associated with all of the metallogenetic processes throughout the Paleozoic, Mesozoic and Cenozoic areas that are also associated with vulcanism (hardrock) and sedimentation (placer) such as during the Miocene and Pliocene metallogenetic epochs and known to carry gold values.

The volcanics, such as andesite, are host rocks for epigenetic quartz veins that can carry both free-milling and gold bearing sulphides. Epigentic gold bearing veins as found withhin the volcanics are epithermal... small and shallow... Hit and miss... (sidebar: Andesite as an example is saturated and does not carry free quartz)... thus if you are in andesite county rock and find small quartz crystals, the q-crystals may have eroded from a quartz vein that carried gold.

What is known as the Colorado Plateau found in the SE of Utah. The NW of New Mexico and a good part of the NE of Arizona; is a capping of non-metalliferous basaltic flows.

Now I have used up my 2-cents... But, I will mention the Gold Bug Pro has bargraph readings that can be usewd to seek out higher concentrations (up to about one+ percent magnetite) of magnetic black sand as expressed in micro-ergs that can be associated with gold in a metallogenetic area known to carry free milling hardrock and placer gold of detectable size.

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Hey Tom & Jim,

I know exactly the country you're talking about, as the Magnetite is very thick, forming pockets on bedrock. If you're using a Mono Searchcoil on a GPX, the only solution is the Enhance or Special/Smooth timing to help balance out the iron. I have had thick pockets of Magnetite mask out 1/2 Dwt nuggets.

It's pretty hopeless for a VLF in this country .... especially a GB2 unless you're going to raise the coil off the ground about 2-3 inches.

A DD searchcoil will normally help, this might be a solution for you.

Rob Allison

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Hey Tom & Jim,

I know exactly the country you're talking about, as the Magnetite is very thick, forming pockets on bedrock. If you're using a Mono Searchcoil on a GPX, the only solution is the Enhance or Special/Smooth timing to help balance out the iron. I have had thick pockets of Magnetite mask out 1/2 Dwt nuggets.

It's pretty hopeless for a VLF in this country .... especially a GB2 unless you're going to raise the coil off the ground about 2-3 inches.

A DD searchcoil will normally help, this might be a solution for you.

Rob Allison

Tks Rob:

The GPX 5000 cuts right through it without a problem. It runs nice and stable.

Im just trying to figure out how to get my dad to find some gold in this kind of stuff. Hes using the GB pro. It just seems to go crazy in this area. But, on a good note, it really helps me pinpoint a small nug when I get over one. :)

Tom

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Howdy All... As Rob notes, Pulses ignore both magnetite and alkali. Thus they are the best choice in the gold bearing metalliferous goldfields that carry magnetite as an accessory mineral.

The standard coil for the Gold Bug Pro is the 5-inch sniper closed frame DD coil, and as Tracker noted, the GB-Pro has a bargraph "dirt strength" scale that measures the concentration of magnetite (black sand)as placer gold is often found associated with gold.

However, as tracker also mentioned, if there is more than about one percent magnetite in the soil, the VLF's are in trouble in the "magnetite-rich" Arizona gold fields.

Where is Trinity AU?... He is really doing great with his GB-Pro...

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Howdy... Correction... I meant placer gold is often found with black sands

More: Black sands consist of magnetite and other darker colored ferromagnesian minerals and has an average sg of about 3.5. If you are detecting in the volcanic county rocka, such as the trachytes and andesites, usually the dirt stength is less the one percent micro-units. Note: If you are in the andsites, trachyites and find small quartz crystals, you are in a possible quartz vein area that may contain placer gold as the andesite and trachytes are saturated and do not carry free-quartz.

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