Measuring your ground mineralization level using a hidden feature of the X70.

[BarnacleBill]

One of the ongoing common mis-conceptions is that the Ground Phase Number(Ground Balance)represents how much mineralization a particular soil matrix contains. The mineralization of course referring to minerals that cause poorer performance of a metal detector, and not a particular quantity of an inert material.

The Minelab X-Terra X-70 has a hidden feature which allows you to make a reasonably accurate assessment of your ground conditions including the iron(Fe3O4, black sand) and/or the conductivity(salinity) of your soil. To clarify, you can quickly measure in relative terms how magnetic or conductive your ground is. You can then jot those numbers down and compare them to any other X70 users in the world.

As a matter of fact a database or registry could be set up to compare your conditions to that of others. Therefore when an X70 user states that they have "high mineralization" which is hampering operation, it can easily be verified whether such is the case.

The procedure is really just an extension of Auto-GBing the X70. So don't become overly concerned that it is terribly complicated, it isn't.

Procedure in Normal GB mode with GB Tracking "OFF" and Sens=20:

A. Auto-noise cancel in the area you will hunting with the coil held 3 feet above the ground and parallel to it.

B. Locate a target free area of soil.

C. Engage Normal GB & remain in the GB screen.

D. Place coil on the soil. Do not press the coil against the ground! This will distort the coil shape and give an inaccurate result. Simply allow the weight of the machine to lightly keep it against the ground.

E. Press the Auto GB button and raise coil about two feet above the ground before Auto GB has completed. If by the time you reach the apex of pulling the coil up to two feet it doesn't complete, then pump up and down from just above the ground to two feet high as accurately as possible. Recall that Auto GB signals with a tone when completed.

F. While still in GB mode press and hold Patterns button to get the numbers. The numbers are six digits in length but read out in three groups of two that will repeat if the Patterns button is held down. Therefore 99 99 99(almost a million) is the largest number possible and 0(00 00 00) is the smallest. Forty-six thousand would appear as the following sequence, 04--60--00. Make a note of the numbers which we will call the "IRON NUMBER"(Magnetite...Black-Sand).

G. As a reference, numbers in the thousands are mild ground, medium grounds tens of thousands , and hot hundreds of thousands. For clarity:

1. 0(zero) >> 10K mild ground.
2. 10K >> 100K medium ground.
3. 100K >> 1M hot to scorching.

Procedure in Beach GB mode with GB Tracking "OFF":

The same as above in normal GB except that your are measuring conductivity. Great for Ocean beaches, salt flats, & dried up lake beds etc. I would also take three samples in the exact same spot and average them to get an average number, using either of the above procedures.

If their is enough interest, then a registry could be started to compare the various ground reports with how stable the detector runs, and effect on depth, correct ID etc. The nine inch default concentric MF should be the only coil used to take the measurements to create a standard. Keep in mind that the X70 may be able to show you why other detectors you own behave in a certain manner based on soil mineralization. It may also provide pertinent information about what equipment you should consider for future purchases.



HH
BarnacleBill

 

[John LA]

n/t

 

[bfodnes]

n/t

 

[pinpointa]

n/t

 

[bfodnes]

Used it today, got several samples, all with 00 first allthough the first one was 22 but an error reading.

Wonder why they keep this wonderful feature in the dark for so long ??

 

[CA Steve]

how did you know that the X-Terra was capable of doing this? What other machines can be used to check mineralization like this?

 

[BarnacleBill]

I didn't come up with the method. The method was explained to me after I made an inquiry regarding some very nasty ground I have in my area. It typically reads in the 300K to 450K range and will cause any VLF, single or multi-freq to go into overload within 6 inches of it.

I am only aware of maybe a White's gold machine and the Fisher F75 that provides any similar type function, but only in the magnetic realm, not conductive. They also have very low resolution comparably.

HH
BarnacleBill

 

[Digger]

Bill, I've been out of town for a few days and just now got back and read your post. Looks like you have been doing some extraordinary tests up there! I have to admit, you peaked my curiousity.


Based on MXT Ground Phase readings of <50, I have always considered my ground to be "moderately mineralized" Not knowing what to expect with the X-70, I took it out to the front yard and gave it a go. Using the 9-inch concentric at 7.5 kHz, Auto NC at an elevation of 24-inches and a sensitivity of 20, I came up with 007732. A number indicating what I would consider to be "mild ground". Although I am not a prospector, wouldn't this procedure be a useful tool for someone wanting to work toward the higher conductive (lower iron) numbers in a black sand environment?

Thanks for the information!! HH Randy

 

[COMMANDR]

Very good info. The database is a super idea. Thanks for sharing.

HH and Keep Swinging

Gary

 

[BarnacleBill]

Hi Randy,

Yes it could be used to track black sand mix. And your readings are what some of the white sand freshwater beaches I hunt come in at. And on those beaches I can run sensitivity up around 28 before I get any chirping, even though they GB around 10.

HH
BarnacleBill

 

[Digger]

Bill, thanks. You have saved me a lot of money. My wife has been asking me to take her to the beach on vacation. Now I can just tell her to go sit in the front yard!


Seriously, I knew my soil was not as hot as many who post here. But I had never thought about comparing it to a beach. No wonder I never found the need for the DD coils on my X-Terras. I like them on some of my other detectors. But that is more due to the fact that they come stock with a DD coil. Being able to compare the concentric "side by side" with the DD on my X-Terras, I've found my concentrics hunt deeper. And now I know why. Thanks for your analysis and tips. HH Randy

 

[Digger]

n/t

 

[parrott]

Hello BB... You did good. The Teknetics T-2 also measures the Fe304 magnetic susceptibility in "Micro-cgs" as does the F-75. The MXT does too, but I'm not familiar with the MXT's procedure or the yardstick used to measure the values.

It is intersting to note that David Johnson was involved in the design of all three, the T-2, F-75 and the MXT. For what is worth, using the T-2 with its standard DD coil, while out nuggethunting in the Mojave desert, over the past 18 momths I have been checking various areas and have only found at worst "Medium mineralization, typical." IMO, I believe it is rapidly changing mineralization that gives the most trouble.

In this area the X-70 with the eliptical 18.75 searchcoil seems to have adequate depth to punch into the "midrange" zone where plus grain-sized nuggets seem(?) to lurk too deep for the plus 50 to 70 kHz "low frequency" gold machines, and too small in size for the PI-types. The upper 6 or more inches below the surface... where the dirt changes in moisture content and seems to tighten-up, but depends upon yearly weather cycles... and may be the upper level of a hardpan or caliche zone.

Later, when the weather is cooler, I will give my X70 a try to measure
ground mineralization... but maybe with the eliptical 18.75 coil. To compare with the T-2 findings. I also have a friend with an MXT. Interesting...

 

[jeff & Maria]

n/t

 

[BarnacleBill]

Hi Parrott,

It's always wonderful to see your posts on ground matrix, it's good for us prospecting wannabe's to learn more should we ever get the chance to stumble through some gold bearing areas. That said, I have seen you post a term several times that I am not familiar with, so what the heck is a "caliche zone"?

I agree with you, and I find in my area it is the variability that causes the most grief for the detectors. One practice I engage in from time to time is to put the X70 in the GB screen with Tracking On, and walk along listening to the ground. Even in "mild" ground the noise level is quite evident as the coil is moved over the surface. This is a great educational exercise to give users an idea of the ground noise that the detector designers have to deal with while picking out valid signals.

And here I may ruffle some feathers, but I left the T2 out as I consider the F75 to really be the "T3". And anyone with an open mind would consider that as a fair statement, as some users acknowledge the heritage going back to the MXT.

One thing I am very curious about and maybe you will be able to find this out in your area, is what roll does saline content play in dry wash or lake bed areas. More plainly, are there areas around you with let's say a medium magnetic signature AND a high saline content that can be read in the conductive beach GB mode? Because the term "hot" ground is very general and could be defined in many ways. High magnetic, high conductivity, high variability, or various combinations of the previous.

HH
BarnacleBill

 

[parrott]

Gosh Mr. BB... I wish I knew as much as you. It has taken me over 70 years to know what I have learned and my poor brain is on overload and
I now am forgetful.

"Caliche" can be found in desert areas. In some fairly level pediments and alluvial fans if present, it is found in thin layers. It sorta follows the surface ground contour and maybe about a foot or two below the surface. It is usually a silty sand that has become cemented with calcium carbonate being deposited through the evaporation of subsurface water being brought to the surface by capillary action. It is alkalin and about 80-percent calcium carbonate. The inpurities can be various oxides of magesium and aluminum. It can be a false bedrock. But over time any nuggets can work into or through the caliche. Normally it is a light cream color and can become exposed on the sides of a slope or by the erosion on top of hill.

I've not experimented with the X70 beach mode, so I cannot answer your
last paragraph. About the T2/F75; I have a T2. It goes deep. But for some reason I did not find any eluvial gold with it after many trips. The first trip out with the X70, and within a few minutes... I found a small nugget. And since then several more while working old piles.

I like using the eliptical DD 18.75 coil. I have removed the skid plate and use the searchcoil agressively in and around the creosote
and small rocks, but careful not to bang it around.

 

[Grant]

cliche your worst nightmare from prospecting to planting a damn rose in your backyard in Vegas! form what I've been told the valley was once a self sustained ocean thus the floor is cliche almost as hard as concrete and just as annoying if you wanna get below it. from my own digging through the desert cliche makes a great runway for gold and below that level well that's the mystery unless your running a mine! Cliche is the reason if Las Vegas had a week of monsoon rain constant it would return to a lake, fine by me I moved for Good reason... J/K , Grant

 

[Thumper III]

Execellent addition for FAQ. Makes me wish I had selected for XT70 with stock instead of purchasing XT50 and extra coil. Thumper III

 

[utmike]

n/t

 

[OB1]

Thanks for this post. I have for many years hunted for very fine alluvial flood gold (too small to be detected). I have noted the gold is deposited in long "runs" along with fine black sands. Find the black sands and you find the gold. The feature mentioned here might be useful in finding and following the alluvial runs.[attachment 95317 B0000171.JPG]
By the way you need a special sluice to recover gold as fine as in the photo.